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COPWIGHT DEPOSIT: 



ELEMENTS OF 
MAMMALIAN ANATOMY 



DAVISON. 



Mammalian Anatomy 



WITH SPECIAL REFERENCE TO 



THE CAT 



ALVIN DAVISON, PH.D. 

EX-FELLOW OF PRINCETON UNIVERSITY ; PROFESSOR OF BIOLOGY IN LAFAYETTE COLLEGE 



WITH OVER ONE HUNDRED ILLUSTRATIONS MADE BY 
W. H. REESE, A.M., FROM THE AUTHOR'S DISSECTIONS 



• t > ) „ ) B 



Study nature, not books." 

!* — Agassis 



PHILADELPHIA 
P. BLAKISTON'S SON & CO. 

1012 WALNUT STREET 
I903 



THE LIBRARY OF 
CONGRESS. 

Two Copies Received 

OCT t 1903 

Copyright EnWy 
CLASS Cl" XXt No 
COPY 0. 



Copyright, 1903, by P. Blakiston's Son & Co. 



WM r. FELL COMPANY 

ELECTROIYPERS, PRINTERS 

PHILADELPHIA, PA. 



PREFACE. 



Huxley after years of pedagogical experience reached 
the conclusion that it is unwise to introduce the beginner 
at once to new and strange forms of microscopic life when 
it is possible to use a subject of which the student is 
bound to know something, — the elementary anatomy of 
a vertebrate animal. The late T. Jeffrey Parker and 
numerous other eminent zoologists likewise advocate be- 
ginning zoological work by studying one of the higher 
animals. Since the majority of college students have 
time for only one year of zoological work, they cannot 
acquire a fruitful knowledge of both vertebrates and 
invertebrates. A study of the former enables one not 
only to become familiar with the anatomy and physi- 
ology of his own body, — a matter of vital importance, — 
but throws a clear light on the significant problem of 
organic evolution such as is not to be derived from a 
study of invertebrate forms. Inasmuch as the genea- 
logical histories are best worked out among the Mam- 
malia, and since a careful study of the anatomy of the 
cat familiarizes one with the anatomy of the human 
body, as is evidenced by the fact that our best medical 
schools now advise their prospective students to dissect 
either a dog, a cat, or a rabbit as a preparation for their 
later work, it is apparent that a knowledge of the mam- 
mals is of the greatest worth. - 

This brief work is intended to acquaint the student 



VI PREFACE. 

with the general structure of the cat, and at the same 
time introduce him to some of the most important mor- 
phologic features of the Mammalia. The following works 
are useful for reference: "Anatomical Technology," 
Wilder and Gage; "Anatomy of the Cat," Reighard and 
Jennings; "Mammals Living and Extinct," Flower and 
Leydekker; "Primary Factors of Organic Evolution," 
E. D. Cope; "Vertebrate Zoology,*' J. S. Kingsley; 
" Anatomie des Hundes," Ellenberger and Baum; 
"Human Physiology," Schenck and Giirber; "Osteology 
of the Mammalia," Flower; " Human Histology," Piersol. 
In the preparation of this book I have consulted a 
large number of works on human and comparative 
anatomy and physiology. Those giving most assistance 
are the works mentioned above, in addition to "Mam- 
malian Anatomy" by Jayne, "Anatomie Descriptive et 
Comparative" by Strauss-Durckheim, " Xervose Central- 
organe" by Edinger, and "Vertebrate Palaeontology" by 
Woodward. I am especially indebted to my artist, Mr. 
W. H. Reese, of the Phillipsburg High School, for the 
care and patience exercised in making the drawings 
from my own dissections. Mr. D. S. Hartline, of the 
Bloomsburgh State Xormal School, has read the entire 
manuscript and made valuable criticisms. Above all, I 
have to thank Prof. J. S. Kingsley for numerous valuable 
suggestions and important corrections in the manuscript. 

Alvin Davisox. 

Easton, Pa., September, rgoj. 



CONTENTS 



PAGE 

Introduction, 17 

The Biological Sciences, 17 

Classification of the Animal Kingdom, 18 

Preparation and Preservation of Material, 20 

General Structure of a Vertebrate, 28 

External Features, 32 

The Skeleton, 36 

General Terms Used in Description of Bones, 36 

Tabulation of Bones, 37 

Structure of Bone, 40 

Bones of the Skull, 41 

Vertebral Column, 57 

Sternum, 63 

Ribs, 65 

Thoracic Limb, 67 

Pelvic Limb. 79 

The Joints, 89 

The Muscles, 93 

Organs oe Digestion, 117 

Alimentary Canal, 117 

Accessory Glands of Digestion, 131 

Peritoneum, 135 

The Vascular System, L 140 

Heart, 140 

Arteries of Trunk. 

Arteries of Neck and Head, 145 

Arteries of Thoracic Limb, 148 

Arteries of Pelvic Limb, 151 

Venous System, 153 

Lymphatic System, 161 

Ductless Glands, 165 

Respiratory System, 168 

Excretory and Reproductive Systems, 174 

Glands of the Skin, 174 

vii 



Vlll CONTENTS. 

PAGE 

Urinary Organs, 174 

Female Organs of Reproduction, 177 

Male Organs of Reproduction, 180 

Nervous System, 186 

Brain, 186 

External Features, 187 

Internal Structure, 192 

Spinal Cord, 205 

Fiber Tracts of the Central Nervous System, 210 

Peripheral Nerves, 216 

Cranial Nerves, 216 

Spinal Nerves, 218 

Sympathetic System, 226 

Organs of Sense, 231 

Cutaneous, 231 

Olfactory, 232 

Gustatory, 232 

Visual, 233 

Auditory, 237 



Index, 243 



LIST OF ILLUSTRATIONS 



FIG. PAGE 

1. Specimen Jar, 20 

2. Injecting Syringe, 21 

3. Diagrammatic View of Operation for Injection, 22 

4. Method of Making Incision in the Carotid Artery for Injection, __ 22 

5. Method of Inserting the Cannula into a Vessel, 23 

6. Palmar Aspect of Cat's Paw with Cannula Inserted, 24 

7. Flat Epithelium Cells from the Mouth, 28 

8. Involuntary Muscle, 28 

9. Cells of Cartilage, 29 

10. Fibers of Voluntary Muscle, 29 

11. Fibers of Connective Tissue, 30 

12. Longitudinal Section of the Humerus of a Kitten, 38 

13. Longitudinal Section of the Femur, 39 

14. Cross-section of Cat's Femur, 40 

15. Diagram of the Bones of the Mammalian Skull Viewed Laterally, 42 

16. Dorsal Aspect of the Cat's Skull, 43 

17. Ventral Aspect of the Skull with the Left Auditory Bulla Re- 

moved, 47 

18. Cut Surface of a Sagittally Bisected Skull, 50 

19. Mesal or Inner Aspect of the Mandible, 54 

20. Ventral Aspect of Larynx, Hyoid Bones, and Tongue, 55 

21. Lateral Aspect of the Skeleton, 58 

22. Plan of a Vertebra, 59 

23. Dorsocaudal Aspect of Atlas, . 59 

24. Lateral Aspect of the Axis, 60 

25. Latero-caudal Aspect of a Thoracic Vertebra, 60 

26. Caudal Aspect of Fourth Lumbar Vertebra, 61 

27. Dorsal Aspect of the Sacrum, 61 

28. Ventral Aspect of the Bones of the Thorax, 64 

29. Caudal Aspect of Sixth Rib, 65 

30. Lateral Aspect of the Scapula, 68 

31. Caudal Aspect of the Clavicle, 68 

32. Cephalic Aspect of the Humerus, 69 

ix 



X LIST OF ILLUSTRATIONS. 

FIG. PAGE 

33. Lateral Aspect of the Ulna, 70 

34. Mesal Aspect of the Radius, 71 

35. Genealogy of the Horse, 73 

36a. Dorsal Aspect of Cat's Manus, 74 

36b. Generalized Type of Carpus, 74 

37. Lateral Aspect of Forelimb of Equus, 75 

38. Lateral Aspect of Innominate Bone, 80 

39. Ventral Aspect of Innominate Bones, 80 

40. Caudal Aspect of Femur, 81 

41. Cephalic Aspect of Tibia, 82 

42. Mesal Aspect of Fibula, 83 

43. Dorsal Aspect of Hind-foot, 85 

44. Diagram of a Diarthrodial Joint, 89 

45. Lateral Aspect of Dissected Knee-joint, 90 

46. Caudal Aspect of Knee-joint, 91 

47. Ventral Aspect of Trunk and Neck Muscles, 99 

48. Lateral Aspect of the Muscles of the Cat, 104 

49. Lateral Aspect of the Muscles of the Thoracic Limb, 105 

50. Mesal Aspect of the Muscles of Thoracic Limb, 112 

51. Ventral Aspect of the Muscles of Trunk and Thigh, 113 

52. Lateral Aspect of the Muscles of the Leg, 113 

53. Caudal Aspect of the Muscles of Crus and Foot, 114 

54. Diagram of the Chief Organs of the Cat, 118 

55. Dorsal Aspect of the Tongue and Larynx, 119 

56. Longitudinal Section of the Canine Tooth, 120 

57. Lateral Aspect of the Permanent Dentition, 121 

58. Ventral Aspect of the Alimentary Canal, 127 

59. Transverse Section of the Cat, 128 

60. Cross-section of the Cardiac End of the Stomach, 128 

61. Gastric Glands, 129 

62. Cross-section of the Small Intestine, 130 

63a. Villi and Glands of Intestine, 131 

63b. Photomicrograph of Intestine with Blood-vessels Injected, 131 

64. Salivary Glands, 132 

65. Photomicrograph of Section of the Liver, 134 

66. Diagram of the Stomach of a Ruminant, 137 

67. Heart Viewed Ventrally, 141 

68. Heart Viewed Ventrally with Caudal Third Cut off, 142 

69. Heart Viewed Dorsally, :__ 142 

70. Chief Arteries of the Trunk, 144 

71. Ventral Aspect of the Arteries of the Head and Neck, 146 

72. Arteries of the Forelimb, 149 

73. Arteries of the Leg, 152 



LIST OF ILLUSTRATIONS. XI 

FIG. PAGE 

74. Cross-section of Artery and Vein, 153 

75. Vein with Valves, 154 

76. Veins of Cat, 155 

77a. Arterial System of a Rabbit, 158 

77b. Arterial System of a Man, 158 

78. Ventral Aspect of Chief Lymphatic Vessels of the Cat, 163 

79. Photograph of the Lymphatic Capillaries and Vessels of Cat's Kar, 164 

80. Diagrammatic Transverse Section of the Chest, 170 

81. Photograph of a Lung Corrosion of a Puma, 171 

82. Termination of a Bronchiole, 172 

83. Ventral Aspect of Female Urogenital System, 175 

84. Median Longitudinal Section of a Kidney. 176 

85. Diagram of Structure of Kidney, 176 

86. Section of Ovary, 179 

87. Ventral Aspect of Male Reproductive Organs, 181 

88. Spermatozoa, 182 

89. Dorsal Aspect of the Brain, 189 

90. Ventral Aspect of the Brain, 190 

91. Diagram of the Ventricles, 192 

92. Sagittal Section of the Brain, 194 

93. Dorsal Aspect of the Brain with the Cerebellum and Portion of 

Cerebrum Removed, 197 

94. Cross-section of the Brain Caudad of the Optic Chiasm, 199 

95. Cross-section of the Brain through Anterior Commissure, 201 

96. Diagrammatic Section of Spinal Cord, 207 

97. Nerve-cell, 208 

98. Diagram of the Relation of Cells and Fibers in the Spinal Cord, 209 

99. Diagram of Some Fiber-tracts, 211 

100. Diagram of Chief Fiber-tracts of the Mammalian Brain, 214 

101. Ventral Aspect of the Brachial Plexus, 220 

102. Ventral Aspect of the Nerves of the Pelvic Limb, 225 

103. Cephalic Half of Sympathetic System, 228 

104. Caudal Half of Sympathetic System, 229 

105. Pacinian Corpuscle, 232 

106. Longitudinal Section of the Eye, 235 

107. Diagram of the Mammalian Bar, 238 

108. Section of the Cochlea of the Calf, 239 



ELEMENTS 



MAMMALIAN ANATOMY 



INTRODUCTION. 

Since this book is designed for the use not only of 
students who have pursued the study of biology for some 
time, but also for those making their first actual acquaint- 
ance with the subject, it may be well to call attention 
to the fact that any animal or plant may be considered 
from several different standpoints. A general study of 
structure and of the relations of the various systems and 
organs is known as Anatomy. Histology concerns itself 
with the cell and cell aggregates or tissues composing 
the organs. These two sciences are included in Mor- 
phology, a term which by many is made to include also 
Embryology or Ontogeny, treating of the development of 
an organism from the egg, or its vegetable homologue, 
to the period of assuming adult characteristics. Since 
ontogeny deals not only with the growth of structure 
but also the process of growth, it may likewise be in- 
cluded under Physiology, a science which has for its 
province the investigation of the functions of the organs 
and systems. A special field of physiology having for 
its consideration the operations, especially the conscious 
z 17 



1 8 ELEMENTS OF MAMMALIAN ANATOMY. 

operations of the nervous system, constitutes the science 
of Psychology. 

The same species of animals are not found in all parts 
of the world. The lion and tiger are found wild only in 
the old world, while the opossum is confined to the new 
world. Again, many species of animals whose fossil re- 
mains indicate their existence on earth several millions 
of years ago, have at present no living representatives. 
A consideration of this geographical and stratigraphical 
location of organisms forms the science of Distribution. 
The science of Phytogeny seeks to discover the geological 
ancestral history of an organism. 

A casual glance shows at once striking similarities and 
differences between the common cat, the lion, and the 
tiger. All have retractile claws, the same number and 
kind of teeth, and the same number of toes. On the 
other hand, the resemblances between these cat-like ani- 
mals and the dogs are less marked, while the differences 
are more striking. The cats and dogs resemble each 
other more closely than either does a horse. Horses, 
dogs, and cats have numerous characters in common 
which are not present in birds. The recognition of such 
resemblances and differences furnishes a basis of classifi- 
cation, the treatment of which forms the science of 
Taxonomy. 

The following is a brief classification of the animal 
kingdom : 

Invertebrata : Animals with no skeletal axis and without a central 
nervous system entirely dorsal of the alimentary 
canal. 

Protochordata : Small marine forms having, during part of their life 
at least, a rudimentary skeletal axis and other features 
marking them as a connecting-link between the inver- 
tebrates and vertebrates. Tunicates or sea squirts, 
Amphioxus. 



INTRODUCTION. 1 9 

Vertebrata: Forms with a skeletal axis and dorsal nerve-cord whose 

anterior end is dilated into a brain. 
Pisces (fish). 

Amphibia (frogs, toads, and salamanders). 
REptilia (snakes and lizards). 
AvES (birds). 
Mammalia (vertebrates suckling their young). 

Prototheria : Oviparous mammals. Ornithorhynchus. 
Eutheria: Viviparous mammals with anus and 
urogenital opening distinct. 
Marsupialia (opossums and kangaroos). 
Insectivora (moles, shrews, and hedge- 
hogs). 
Edentata (sloths and ant-eaters). 
Chiroptera (bats and flying foxes). 
Rodentia (rabbits, squirrels, mice, and 

rats). 
Cetacea (whales, porpoises, and dol- 
phins). 
Sirenia (sea cow). 
Ungulata (the hoofed mammals). 
Carnivora (dogs, cats, wolves, and 

foxes) . 
Primates (monkeys and man). 



A glance at the above outline shows that the class 
Mammalia is divided into two subclasses, the latter of 
which includes ten orders. Each of these orders consists 
of several families which in turn are composed of genera 
made up of species. The order Carnivora includes eleven 
families, of which Canidae (the dogs), Felidae (the cats), 
and Ursidae (the bears) are the most frequently seen in 
America. The family Felidae is represented by only two 
living genera, Cynaelurus and Felis. The genus Felis 
includes several species, of which Felis leo (the lion), 
Felis tigris (the tiger), and Felis domestica (the cat) 
are the most familiar. Of the last species, there are sev- 
eral varieties, such as Maltese, Angora, and Manx cats. 

Linnaeus, born in Sweden, 1702, invented the system 



20 ELEMENTS OF MAMMALIAN ANATOMY. 

of binomial nomenclature in accordance with which the 
scientific name of every plant and animal is composed of 
two parts, the generic and specific. Thus the house cat 
is designated Felis domestica; the lion, Felis leo; the 
dog, Canis familiaris; the wolf, Canis lupus; the pig, 
Sus scrofa; the red deer, Cervas elephas; the elephant, 
Elephas Africanus; the ourang-outang, Simia satyrus; 
and man, Homo sapiens. 



METHODS OF PRESERVING MATERIAL. 

Alcohol has been widely used as a preservative, but 
owing to the fact that it is expensive and quickly evap- 
orates from the specimen exposed to the air, thereby 
rendering the parts dry and brittle, its 
use has been largely supplanted by for- 
malin. Formalin, CH.,0, is often sold 
under the names of formose, formol, 
formine, formalosa, and formaldehyd. 
It can be purchased for about thirty 
cents a pound. For preserving any ani- 
mal or plant, the concentrated 40% for- 
Jar PECIMEN maldehyd is diluted with water in the 
proportion of ninety-five parts of the 
latter to five parts of the former. It is evident, there- 
fore, that one pound of formaldehyd will make about 
ten liters of preserving fluid. 

The specimens may be kept a year or two without 
changing the formalin in ordinary stone jars with covers, 
but for permanent preservation the glass jar with the 
ground-glass cover should be used (Fig. 1). 

Preparation of Vascular System. — To render the vessels 
plainly visible and distinguish the arteries from the 
veins, it is advisable to inject the former with a red 




INTRODUCTION. 



21 




R 



mass and the latter with a blue mass. These fluid masses 
should be of such a character as to harden in a short 
time after injection, so that they will 
not run out when the vessels are cut 
during dissection. 

A syringe of hard rubber, having a 
capacity of about two ounces, serves 
very well for injection. A cannula of 
correct size may be had by asking the 
druggist for the filling cannula of the 
Parke Davis serum syringe. The end 
to be inserted into the blood-vessel 
should be ground off obliquely and 
smoothly on a whetstone. The connec- 
tion between the cannula and nozle is 
formed by stiff rubber tubing which 
should be securely tied to the cannula 
(Fig. 2). 

The injecting mass is prepared by 
thoroughly mixing 100 c.c. of water, 20 
c.c. of glycerin, 20 c.c. of concentrated 
formalin, and 85 gm. of common laun- 
dry starch. One-half should be colored 
red by adding to it one or two grams 
of powdered carmin made into a paste 
with a few drops of ammonia, and the 
other colored blue by dissolving in it a 
gram or two of soluble Berlin blue. 
These liquid masses, after being passed 
through a fine wire strainer or a coarse 
piece of cheese-cloth stretched across a 
funnel, may be preserved for any length of time in covered 
jars. 

The animal may be anesthetized by placing it in a 



H 



Fig. 2. — Injecting 
Syringe. X i. 

p, Plunger handle; 
b, barrel; pi, 
nozle ; c, cannula ; 
r, rubber tube ; dt, 
point of detach- 
ment; s, string. 



ELEMENTS OF MAMMALIAN ANATOMY. 




t box with a cloth or absorbent cotton wet with 30 
c.c. of ether or chloroform. If only the arteries are to 

be injected, the cat may re- 
main in the box until dead ; 
but if the veins are also to 
be injected, it is preferable 
to use ether for the anes- 
thetic and then remove the 
animal to the tray as soon 
as it is unconscious, and re- 
flect a portion of skin, ex- 
posing the external jugular 
veins (Fig. 3). With the 
curved forceps thrust be- 
neath the vein a cord may 
be pulled through and tied 
in a loose knot. One-half 
inch from the latter a 
second cord should be tied 
around the vein loosely. An 
oblique cut (Fig. 4) with the 
point of the scissors directed 
caudad is then made in the vein between the cords. The 
incision should extend about 
half-way through the vessel. 
Absorbing the blood with ab- 
sorbent cotton as it runs from 
the vessel will prevent clog- 
ging. If too much ether has 
not been used, the blood will 
continue running fifteen min- 
When it has nearly 
sed flowing, the carotid 
artery must be found bv making a slit in the muscle 



Fig. 3. — Diagrammatic View of 
Operation for Injection. 

d, Broken line showing course of the 
carotid artery beneath ; b, string 
loosely tied; c, transverse vein 
uniting external jugulars; a, 
points of curved forceps con- 
taining string. 




Fig. 4. — Method of Making In- 
cision in the Carotid Ar- 
terv for Injection. 



INTRODUCTION. 



23 



alongside of the trachea just mesad of the jugular, as 
indicated by the line d (Fig. 3). Having cut through 
the muscle, two white cords are seen along either side 
of the trachea. The mesal one may be red, as it is the 
carotid artery. The lateral one, lying in the same sheath 
with the preceding, is the vagus or tenth cranial nerve. 
Separate the artery from the nerve and tie two cords 
loosely around the vessel as in the case of the jugular. 
Lift up the artery with the index finger (Fig. 4), and 
make an oblique incision with the 
scissors. The cannula with the con- 
necting tube attached should then be 
inserted caudad in the oblique cut of 
the artery (Fig. 5), and the string s 
drawn tight so as to hold the cannula 
in place. The string st should then 
be tightened to prevent the injection 
mass from running out where the can- 
nula is inserted. After stirring the red 
mass, filling the syringe, and slipping 
the nozle into the connecting tube the 
operator should press slowly but con- 
tinuously on the plunger until that 
portion of the carotid cephalad of the 
string st is well distended. In a large 
cat this will not occur until the syringe is nearly or quite 
empty. When the vessels are full, the cannula is with- 
drawn while the operator pulls on both ends of the string s. 
The syringe must be washed out immediately, after which 
the blue mass is well stirred and injected caudad into the 
external jugular in the same manner as described for the 
arteries. 

By making a slit about three inches long in the ab- 
dominal wall a fold of the intestine may be pulled out 




Fig. 5. — Method of 
Inserting the Can- 
nula into a Ves- 
sel. 



24 ELEMENTS OF MAMMALIAN ANATOMY. 

so that its lumen can be filled with about 200 c.c. of 
15% formalin. The same amount should be injected 
into the lungs by inserting the cannula caudad into 
the ventral wall of the trachea. If the cat is not to 
be used at once, it may be preserved several months 
by wrapping it in a piece of muslin saturated with a 
solution of thymol (thymol, 5 gm., dissolved in 200 
c.c. of hot water). Thymol is a fungicide. An outer 
wrapping of well-vaselined cloth prevents evaporation 
in case the specimen is kept in a dry room. 

The portal system is not injected through the jugular 
vein. The portal trunk just caudad of 
where it enters the liver may be found 
by cutting a piece from the abdominal 
wall on the right ventral aspect just 
caudad of the last rib. After two loose 
knots are tied around this trunk as 
directed for the jugular, the cut is made 
and the cannula inserted caudad. About 
- Palmar j 5 cc - °f the blue mass may be injected 

Aspect of Cat's into the portal system of a large speci- 
Paw with Can- _ . . J . . . . . , ... 

nula Inserted. men. This should not be injected until 

the other systems have been filled. 
The lymphatic system must likewise be injected for 
demonstration. While the cat is being anesthetized, 5 
gm. of soluble Berlin blue are dissolved in 100 gm. of 
water, and the solution warmed to about the tempera- 
ture of the body. As soon as the cat is unconscious 
the syringe should be warmed by filling it with hot 
water, and the point of the cannula pushed obliquely 
proximad under the thick skin on the palm (Fig. 6) 
of the paw. The syringe after being half filled with 
Berlin blue solution is attached to the cannula and the 
plunger pushed in very slowly so that one-fourth of the 




INTRODUCTION. • 25 

amount in the syringe is forced out in ten minutes. 
While the injection is being made the limb should be 
gently massaged by pinching and rubbing from the 
foot toward the body. This facilitates the flow of the 
liquid in the lymph- vessels. In this manner the lymph- 
atics of each limb are filled. The author has been 
able to fill the left thoracic duct by continuing the in- 
jection for about twenty minutes in the palm of the 
left paw. The lymphatics of the head and neck may 
be injected in a similar manner by inserting the cannula 
beneath the skin on the tip of the ear, the tip of the 
tongue, the tip of the nose, and the lips. 

In order to inject the lacteals the abdominal cavity 
must be Opened, and the cannula inserted very obliquely 
into the wall of the small intestine so that its point is 
between the mucous and muscular coats. The half- 
filled syringe being attached, very gentle pressure should 
then be exerted on the plunger, until the blue solution 
appears in the lacteals. To inject all the lacteals it is 
necessary to insert the cannula into the wall of the 
intestine at a dozen different places. To fill the thoracic 
duct injection may be made into the large lymphatic 
gland lying at the point where the converging blood- 
vessels of the mesentery meet. The best solution for 
injecting the thoracic duct is made by dissolving 7 
gm. of gelatin in a warm Berlin blue solution (4 gm. 
of Berlin blue to 100 c.c. water). This should be filtered 
through a single layer of absorbent cotton and then 
injected while still quite warm. In all cases injections 
to fill the lymphatics must be warm and must be pushed 
in very slowly. These lymphatic injections are best 
preserved by injecting the trachea and intestine with 
95% alcohol and immersing the cat in a jar of 70% 
alcohol. 



26 ELEMENTS OF MAMMALIAN ANATOMY. 

Preparation of a Mammal for Dissection of the Muscles, 
Peripheral Nerves, and Viscera. — The simplest method 
is to anesthetize the animal as before described, remove 
the skin, make a slit throughout the entire ventral 
body- wall, and immerse the specimen in a jar of 5% 
formalin. A better method is to inject into the carotid 
artery 200 c.c. of glycerinated formalin (water 140 
c.c, glycerin 30 c.c, formalin 30 c.c), and half that 
amount into the intestine and trachea. The specimen 
may then be preserved in the thymol and vaselin cloths 
as previously described, or put into formalin. 

Preparation of the Central Nervous System. — The 
animal may be killed either with chloroform or ether. 
About 200 c.c. of formal-bichromate (170 c.c of 5% 
potassium bichromate and 30 c.c. of formalin) are then 
injected slowly cephalad into the carotid artery (Figs. 3, 4, 
and 5). After skinning, the eyes should be cut out 
and the flesh removed from the head and dorsal side 
of the vertebral column. On a line connecting the 
caudal borders of the orbits, cut through the skull to 
the brain with the bone cutters and remove piece by 
piece the roof of the skull. Next cut away the lateral 
walls down to the base of the brain. Care must be 
exercised in laying bare the cerebellum, and cutting 
loose the tentorium cerebelli, the plate of bone separating 
the cerebrum from the cerebellum. The spinal cord 
is next laid bare dorsally, beginning with the atlas, by 
cutting through the pedicles of the neural arches on 
either side. With a sharp knife or a pair of scissors 
the spinal nerves may then be cut and the cord lifted 
from behind forward out of its bed, until the brain is 
reached. The latter must be carefully raised while the 
nerves at its base are cut, and the dura mater loosened. 

To further harden them the brain and cord should 
be placed in weak formal-bichromate (5% formalin, 500 



INTRODUCTION. 2 7 

c.c. -f 5% potassium bichromate, 500 c.c.) one week. 
in the dark: ~T Ivight causes a precipitate. At the end 
of one week: the specimen should be placed in 1000 
c.c. of 5% formalin for another week, after which it is 
ready for dissection. In case brains of calves or sheep 
are used a hammer and bone chisel are necessary for 
opening the skull. The head should first be nailed to the 
tray. As soon as the brain is removed it should be 
placed in a large pan of water and the dura mater care- 
fully cut away, the clotted blood washed off and a 
syringeful of strong formal-bichromate injected into the 
third ventricle by pushing the cannula about half an 
inch through the infundibulum (Fig. 94). The brain 
of a sheep or calf will be very soft when removed, as it 
cannot be hardened previously by injecting the harden- 
ing fluid into the arteries. Therefore it is necessary 
to lay the specimen on absorbent cotton in the jar 
of formal-bichromate, which must be exchanged for 
fresh fluid on the second and third days. At least two 
weeks are required for hardening the brain of a sheep or 
calf, after which it is placed in 5% formalin for a week 
or more to wash out the bichromate before dissection. 
Brains are best preserved permanently in 85% alcohol. 

Preparation of the Osseous System. — A mounted skele- 
ton of the cat may be purchased for about eight dollars. 
A partially articulated skeleton may be easily prepared in 
the laboratory by cutting most of the flesh from a speci- 
men soaked in formalin two weeks. After drying a few 
days the remaining tissue is easily removed from the 
bones, which will remain articulated if the ligaments at 
the joints are not cut. Clean disarticulated bones are 
best secured by following directions given in the ' ' Ana- 
tomical Technology " by Wilder and Gage. A beautifully 
cleaned set of bones may also be obtained by exposing 
to the weather during the summer the skinned carcass. 



GENERAL STRUCTURE. 

The study of any vertebrate reveals the presence of 
numerous organs, each of which is for the performance 
of a particular function. Thus the heart is the organ 
for the propulsion of the blood, the kidney for the elim- 
ination of the nitrogenous waste. Several organs com- 
bined for a common purpose constitute a system. The 
heart, with the various vessels for conveying the blood, 
forms the circulatory system. The following eight 
systems are found in all Mammalia: Osseous or bony, 




Fig. 7. — Flat Epithelium Cells Fig. 8. — Involuntary Muscle- 
from the Mouth. X 150. cells. X 250. 

n, Nucleus of the cell. n, Nucleus of a cell. 

muscular, digestive, respiratory, vascular, excretory, re- 
productive, and nervous. 

The relative locations of the various systems are 
represented diagrammatically in Fig. 54. The organs 
have the same arrangement throughout all the orders 
of mammals. Moreover, the minute structure of the 
same organ is so similar in the different species that in 
most cases one can scarcely distinguish them by micro- 
scopic examination. The organs are composed of four 

28 



GENERAL STRUCTURE. 20 

classes of tissues: Epithelial, which covers all free sur- 
faces; connective, forming the bones, binding together 
the muscular fibers and elements of the nervous system 
and making up cartilage and ligaments (Fig. n); mus- 
cular, composing the greater part of the 
muscular system; and nervous, consti- ^ 

tuting the nervous system (Fig. 85). . .. 

The naked eye is unable to distin- 
guish the elements of the tissues, but 
the microscope reveals the fact that 
each kind of tissue is formed of either Fl S; ^;~^ s °5 
cells or fibers or, as is most frequently 150. 
the case, a combination of both. 

The different relative arrangements of these anatomic 
elements, together with their morphology, permit one 
to know from what organ any particular section of 
tissue under consideration has been taken. 

These ultimate units of structure are still further 
resolved into parts by the chemist, who 
has shown that they are composed 
largely of carbon, hydrogen, oxygen, 
and nitrogen. Since there can be no 
energy developed in the body without 
the disintegration and consequent death 
of some of the particles composing the 
Fig. 10. —Fibers millions of tiny cells, it is plain that 

Uvsc^xioo tlie y must have tlieir losses replaced in 
n, Fiber ; t, tendon, order to continue their existence. There- 
fore a method of preparing the food for 
the use of the cells, and a way of transporting it to each 
of them are necessary. 

The former is accomplished by the digestive system, 
which, through the agency of the salivary, gastric, 
pancreatic, and other glands, transforms the food into 




3° 



ELEMENTS OF MAMMALIAN ANATOMY. 



a special liquid state capable of being absorbed by the 
millions of minute finger-like villi of the small intestine 
(Fig. 63). Thence it is transferred by the lacteal vessels 
and veins to the heart, whence it is conveyed by the 
arteries to their capillary distribution in the neighbor- 
hood of every cell in the body. 

The dead matter or waste material resulting from the 
cell activity is of two kinds, gaseous and liquid. Both 
diffuse through the capillary walls into the blood. The 




Fig. 11. — Fibers of Connective Tissue. X 300. 



former, which is carbon dioxid, is carried to the heart 
and thence by the pulmonary arteries to the lungs, where 
it passes into the terminal branches of the trachea, and 
finally by expiration reaches the exterior. The liquid 
excretion is transported by means of the veins and arte- 
ries to the kidneys, where it diffuses through the walls 
of the capillaries into the minute tubules opening into 
the ureters leading to the bladder. It must be remem- 
bered that the material known as feces passed out of 
the alimentary canal through the anus is not an excretion 



GENERAL STRUCTURE. 3 1 

of the cells of the body, but merely that portion of the 
food not transformed into a condition permitting it to be 
absorbed by the villi. 

In addition to these systems necessary for the main- 
tenance of life, the cat requires a means for supporting 
the body and moving about, furnished by the osseous 
and muscular systems. The osseous system serves not 
only for support and locomotion, but also for the pro- 
tection of the delicate vital organs. The skull and spinal 
column contain the brain and spinal cord, while the 
heart and lungs are well shielded by the dorsal vertebrae, 
the ribs, and sternum. Likewise the muscles ward off 
serious injuries from the blood-vessels, as they cover to 
a considerable depth nearly all large arteries, and also 
aid by their contraction in moving the lymph through 
the numerous lymphatic vessels extending from the 
extremities to the jugular veins. 

These systems previously described are capable of per- 
forming their functions only when supplied with nerves 
through which impulses can be transmitted from the 
brain and spinal cord. Stimuli sent by the brain or cord 
through the nerves cause the gastric juice to flow into 
the stomach, the bile and pancreatic secretions to be 
formed and poured forth into the intestines, the kidneys 
to eliminate the waste from the blood, the heart to beat, 
and the muscles to contract and relax. 

The only system which is not absolutely necessary to 
the life of the cat is the reproductive ; but this is required 
for the continuance of the species. It is not, however, 
functional during the entire life, but as a rule only from 
the end of the first to the tenth year. 



32 ELEMENTS OF MAMMALIAN ANATOMY. 

PRACTICAL QUESTIONS AND SUGGESTIONS. 

1. What advantages are derived from the study of mammalian anat- 
omy? 

2. Define morphology and state a fact from that science. 

3. What two sciences does biology include? 

4. What five sciences are included in zoology? 

5. Make a physiologic statement concerning the heart. 

6. State five facts belonging to the science of distribution. 

7. What is taxonomy? 

8. Name five classes of vertebrates. 

9. By examining specimens discover what external feature distin- 
guishes a reptile from an amphibian. 

10. Do all mammals have hair? 

1 1 . What habit is common to no other vertebrates except mammals ? 

12. Give two points of difference between the two subclasses of Mam- 
malia. 

13. Name the ten orders of Eutheria and give an example of each. 

14. Which orders derive their names from the habits of the animals? 

15. Which orders derive their names from anatomic features? 

16. Which orders are aquatic? 

17. What is the ultimate syllable of all family names? 

18. Explain what is meant by binomial nomenclature. 

19. Name three families of Carnivora. 

20. Examine specimens and determine wherein the teeth of Canidae 
differ from those of Felidae. 

21. What two rank names constitute the scientific name of an animal? 

22. Give the scientific name of five Carnivora, two Ungulata, and two 
Primates. 

23. Define organ, system, tissue, and cell. 

24. Name two organs belonging to each system. 

25. How do the elements of the four kinds of tissue differ? 



EXTERNAL FEATURES. 

The cat, like all other mammals, possesses two well- 
defined skeletons, the endoskeleton, consisting of the true 
bones, and the exoskeleton, composed of the skin and its 
appendages. The skin invests the body completely and 
is continuous with the lining of the digestive and uro- 
genital canals. It varies in thickness in different regions, 
being very thin on the lips, ears, and eyelids, and ex- 



GENERAL STRUCTURE. 33 

ceedingly thick on the pads of the feet and on the ventral 
neck region, where, in contest with an enemy, it is most 
likely to be seized. A fibrous connective tissue binds the 
skin to the subjacent structures. In some places the 
union is very firm, as on the distal parts of the limbs 
and the head, while in other regions it is loose, as on 
the lateral aspect of the trunk. 

The skin consists of an external layer, the epidermis, 
and, beneath this, the dermis or true skin, designated the 
corium. The epidermis is composed of numerous strata 
of epithelial cells. Those on or near the surface are 
much flattened while the deeper ones are more or less 
cubical. As the superficial layer desquamates in minute 
fragments, forming what is commonly called dandruff, 
it is replaced by cells developed from the deeper layers. 

The portion of the epidermis adjacent to the corium 
or cutis vera contains the coloring-matter of the skin, 
and is known as the rete mucosum. At the orifices of 
the internal passages, such as the digestive and genital 
tracts, the epithelium changes to a soft delicate nature, 
and is then known throughout these passages as mucous 
membrane. 

The corium or dermis is a form of fibrous connective 
tissue whose deepest portion forms the white fluffy 
areolar substance cut in removing the skin. In many 
regions just below the true skin is a layer of adipose 
tissue, which when examined under the microscope is 
seen to be composed of numerous globular fat-cells sup- 
ported by fibrous areolar tissue. The seven pads on the 
forepaw and the five on the hind one consist of greatly 
thickened epidermis, the corium, and masses of fibrous 
connective tissue enveloping many fat-cells. 

The sebaceous or oil glands lie in the corium, and by 
means of a duct open into the hair follicle near the sur- 

3 



34 ELEMENTS OF MAMMALIAN ANATOMY. 

face. The sudoriparous or sweat glands, composed of 
coiled tubes, are present in the subcutaneous tissue, from 
whence a duct extends to the surface. Although there 
are no blood-vessels in the epidermis, numerous nerve 
terminations are present in the deeper portions. The 
true skin is richly supplied with both nerves and blood- 
vessels. 

The claws produced by a special modification of the 
epidermis are among the most important appendages of 
the skin. Five of these are present on each forefoot, 
while only four occur on the hind one. At the root of 
each claw, the dermis forms a crescentic fold over it, and 
beneath is a number of papillae richly supplied with 
blood-vessels. This entire structure forms the matrix of 
the claw, which is set around the terminal part of the 
distal phalanx of each digit. Claws, or some similar 
structures, such as nails or hoofs, are present in all 
mammals except the Cetacea. 

Another important appendage of the skin is the hair, 
which covers the entire body except the tip of the nose 
and the pads of the feet. Its length and color vary 
with the variety of the cat. The Mombus cat of Africa 
has short stiff hair, while the Angora or Persian cat is 
remarkable for the length and delicacy of its soft fur. 
The hair, like the nails, is an extreme modification of 
the epidermis. Each hair grows from a papilla at the 
bottom of a small sac, the follicle, which is a depression 
in the corium. The central part of the hair is the pith, 
and the external portion, formed of thin overlapping 
scales, the cuticle. The coloring-matter lies in the super- 
ficial scales, and may be disposed in such an irregular 
manner that one-half of a hair is white, and the other 
half yellow. 

The large hairs on either side of the nose are known 



GENERAL STRUCTURE. 35 

as vibrissa?. Their roots are provided with delicate nerve- 
endings of touch, so that the animal may find its way 
with ease through dark narrow passages. There are a 
few long hairs above the eyes, forming the eyebrows, but 
no eyelashes are present. 

Most of the hairs are inserted obliquely into the skin, 
but when angered the cat can erect them by the con- 
traction of a small muscle passing from the skin to the 
hair-bulb. 

On some mammals the hairy covering is partial and 
limited to particular regions; in others, as the hippopota- 
mus and the Sirenia, it is very scanty, but scattered over 
the whole surface; while in the Cetacea it is reduced to a 
few small bristles about the mouth. 

Some kinds of hair, as those of the mane and tail of 
the horse, are shed and renewed annually. Most mam- 
mals have a long hairy coat in winter which gives place 
in spring to a short coat. The Arctic fox, hare, ermine, 
and numerous other animals of the colder regions undergo 
a complete change of color in the two seasons, being 
white in winter and brown or gray in summer. By this 
protective coloration they escape many of their enemies. 



THE SKELETON. 

The number of bones in the skeleton of the cat varies 
with its age, since two or more bones separate in the 
young may form one mass in the old animal. The three 
portions of the innominate bone which are distinct (Fig. 
38) in the young, become fused in the adult. In very old 
age many sutures of the skull become partially or wholly 
obliterated. In the young adult cat the number of bones, 
exclusive of the teeth, ear bones, chevron bones, and 
sesamoid bones, is about 233. The sacrum is reckoned 
as one bone, though composed of three coalesced verte- 
brae. The structure and embryology of the teeth show 
that they belong to a different category from the bones. 
The ossicula auditus, or ear bones, are the malleus, incus, 
and stapes of the middle ear. The chevron bones are 
eight in number, attached to the ventral side of the 
vertebrae of the tail. The sesamoid bones number about 
forty, of which the patella, or knee-cap, is the largest. 
They are formed in the tendons where there is much 
pressure or friction, as upon the volar surface of the 
metacarpus. The outline on page 37 gives the classifica- 
tion, names, and number of the different bones of the 
skeleton. 



GENERAL TERMS USED IN DESCRIPTION OF BONES. 

In reference to shape the bones are spoken of as long, 
short, flat, and irregular. Long bones are those having a 
shaft or diaphysis in which is a cavity filled with marrow, 
and two enlarged extremities or epiphyses (Fig. 13): 

36 



Skull 



Head 



Axial Skele- 
ton 



Trunk 



Thoracic limb 



Appendicular 
Skeleton 



Pelvic limb 



Frontal, 2 

Ethmoid, 1 

, Temporal, 2 

I Parietal, 2 

Interparietal, . . . . 1 

Occipital, r 

Sphenoid 1 

Premaxillary, ... 2 

Maxillary, 2 

Palatine, 2 

, Vomer, 1 

< Maxilloturbinal, . . 2 

Nasal, 2 

Lachrymal, 2 

Malar or Jugal, ... 2 

Mandible, 1 

iTympanohyal, ... 2 

Stylohyal, 2 

Epihval, 2 

Ceratohyal, 2 

Basihyal, 1 

Thyrohyal, 2 

/ Cervical vertebras, . 7 

\ Thoracic vertebrae, . 13 

Vertebral column / Lumbar vertebrae, . 7 

j Sacral vertebrae, . . 1 

( Caudal, 21 

f Ribs, 26 

Thorax t Sternum, 1 

Shoulder girdle { Scapula, 2 

( Clavicle, 2 

Arm Humerus, 2 

Forearm f Ulna, 2 

\ Radius, 2 

, Scapholunar, .... 2 

/ Cuneiform, 2 

\ Pisiform, 2 

_ ( Trapezium, 2 

Carpus ) Trapezoid, 2 

( 1 Magnum, 2 

* Unciform, 2 

/ Metacarpus 10 

Phalanges f J*P*\ ma J I0 

< Middle, 10 

( Distal, 8 

Pelvic girdle Innominate, .... 2 

{Femur, 2 

Patella 2 

Tibia 2 

Fibula, 2 

! Astragalus, .... 2 

Calcaneum, .... 2 

Scaphoid, 2 

Entocuneiform, . . 2 

Mesocuneiform, . . 2 

Ectocuneiform, ... 2 

Cuboid, 2 

Metatarsus 10 

_, , f Proximal, 8 

Phalanges J Midd i e 8 

( Distal 8 

37 



Hand 



Foot 



38 



ELEMENTS OP MAMMALIAN ANATOMY. 



femur, fibula, metacarpals, and phalanges. Short bones 
are those not elongated and with no medullary cavity: 
tarsus and carpus. Flat bones are plate-like, with a layer 
of cancellous tissue between two 
layers of compact tissue: parietal, 
scapula, and innominate. Irregular 
bones are those which have an ex- 
ceedingly irregular shape: ethmoid 
and vertebrae. The aspect of a bone 
is the portion seen when viewed from 
a given direction. The border of a 
bone is the margin, edge, or ridge at 
the juncture of two surfaces. Proxi- 
mal is used to designate the portion 
of a structure nearer the axis or spinal 
column, in distinction to distal, which 
signifies the part farther removed 
from the axis. Cephalic indicates the 
part of an organ nearer to the plane 
passing just beyond the head and per- 
pendicular to the spinal axis, while 
caudal is applied to the other part of 
the organ nearer to the perpendicular 
plane at the end of the extended tail. 
Sagittal refers to the plane bisecting 
the animal in a vertical and longitu- 
dinal direction. Mesal and lateral are 
adjectives, the former meaning nearer 
to the sagittal plane and the latter 
more remote on either side of that 
plane. Proximad, distad, cephalad, 
caudad, mesad, and laterad are adverbs 
indicating direction in accordance with the adjectives to 
which thev are related. 




LOXGITU- 

Section of 
the Humerus of a 
Kittex. 
h, Epiphysis for head; 
c, cartilage ; b, bone ; 
vi, medullary sub- 
stance; o, epiphysis 
for olecranon pro- 
cess. 



THE SKELETON. 



39 



A process is a projection or elevation. 

A tuberosity is a rough obtuse pro- 
cess. 

A tubercle is a small and usually more 
or less pointed process. 

A condyle is a rounded and somewhat 
elongated smooth articular process. The 
distal end of the femur presents a pair 
of condyles (Fig. 40). 

A fossa is an irregular depressed area 
(Fig. 30). 

A foramen is an aperture for the pas- 
sage of vessels or nerves. 

The shaft is the body or middle por- 
tion of an elongated bone. 

The head is a spheroidal prominence 
at one end of an elongated bone (Fig. 
40). 

The epiphysis is a small process of 
bone ossified from a separate center. In 
the young animal it is attached to the 
main bone by cartilage, but in the adult 
becomes a part of the main bone (Fig. 
12). The femur has four epiphyses, one 
for the head, one for the distal extremity, 
and one for each trochanter process (Fig. 
40). With the exception of the pha- 
langes, metacarpals, and metatarsals, all 
of the long bones have an epiphysis at 
each extremity. In the human, these 
epiphyses do not unite with the shaft 
before the sixteenth year. Diploe is 
the spongy layer of bone between the 
layers of the flat bones (Fig. 18). 



&. 



mm 



rnd 




Fig. 13. — Longitu- 
dinal Section 
of the Femur. 

md, Medullary cav- 
ity ; d and h, can- 
cellous tissue; tr, 
cancellous tissue 
of trochanter pro- 
cess ; b, compact 
bony tissue. 



compact surface 



40 ELEMENTS OF MAMMALIAN ANATOMY. 

The articulation of a bone has reference to its contact 
with other bones by means of joints. 



STRUCTURE OF BONE. 

Every bone is completely covered except on its articu- 
lating surfaces with a tough membrane, the periosteum, 
which serves for the attachment of muscles, and the 
renewal of bony tissue in case of injury. The long bones 
contain a cavity, the medullary cavity, filled with marrow 




Fig. 14. — Cross-section of Cat's Femur. X 5. 

cp, Compact tissue ; en, cancellous tissue ; en, endosteum ; mc, medullary 

canal; pe, periosteum. 

(Fig. 12). This cavity is lined with endosteum, a mem- 
brane similar to the periosteum. 

The shaft of the long bone is composed mainly of 
compact bony tissue through which extend longitudin- 
ally intercommunicating microscopic channels, Haversian 
canals, for the conveyance of blood-vessels, nerves, and 
lymphatics. 

The lacuna, or spaces for the bone cells during life, 
are arranged concentrically about the Haversian canals. 
The canaliculi, or processes of the lacunae, communicate 



THE SKELETON. 41 

with one another. At the extremities of the bones the 
place of the medullary canal is taken up by cancellous 
tissue (Fig. 13, d), the compact tissue being very thin. 
The flat bones have no medullary canal, but the diploe 
or cancellous tissue lying between the outer compact 
tissue has its spaces filled with a red marrow of the same 
nature as that in the cancellous tissue of the long bones, 
wherein the red blood-corpuscles are formed. The large 
medullary cavity or canal is filled with yellow or fatty 
marrow. 

BONES OF THE SKULL. 

The skull is usually considered in two parts, r the 
cranium and face. The former is composed of nine 
bones, which will be described in order. 

The frontal bones (Figs. 15 and 16) are two in number, 
lying between the orbits, and articulating with one 
another in the median line. They form the roof of the 
cephalic part of the brain cavity and the caudal portion 
of the roof of the nasal chamber. A lateral projection 
(po, Fig. 16) is known as the postorbital process. Within 
the frontal bone is a cavity, the frontal sinus (Fig. 18), 
which contains air and is lined with mucous membrane. 
It communicates with the nasal cavity. The lateral 
descending portion of the bone, articulating with the 
palatine and orbit osphenoid, is the orbital plate of the 
frontal. 

In the majority of the Mammalia the frontal is a 
paired bone, but in man the two portions become anchy- 
losed during the fifth or sixth year. The horns of 
ruminants are outgrowths of these bones. Among the 
Cervidae (deer) horns are usually developed only on the 
male, and are shed every year. In the Bovidae (cattle) 
the horns are permanent when present. 



42 ELEMENTS OF MAMMALIAN ANATOMY. 

The ethmoid (Fig. 18) is a single bone lying ventral 
to the frontals and nasals. It separates the cranial 
cavity from the nasal cavity and projects into the latter 
in the form of two thin scroll-like plates of bone and a 
median vertical plate. In order to see the relations of 
this bone, three skulls must be used, one of which should 







p-m% TtLajt-illary h 



*#>^ 



Fig. 15. — Diagram of the Boxes of the Mammalian Skull Viewed 

Laterally. 
1, 2, 3, etc., indicate the places of exit of the twelve cranial nerves, pmx, 

Premaxillary ; ty, tympanic, 7 and 8 are on periotic; thy, tympano- 

hyal; shy, stylohyal; ehy, epihyal; chy, ceratohyal; bhy, basihyal; 

thhy, thyrohyal. The cartilage bones are shaded. — (From Fl 

after Huxley.) 



be bisected sagittally, a second should have the roof 
of the cranial and nasal cavities removed, and the third 
should be cut transversely on a line joining the middle 
of the orbits. The ethmoid is usually visible externally 
as a small rhomboid plate on the mesal wall of the orbit 
between the frontal, lachrymal, and palatine bones. It 
consists of four parts: the paired ethmoturbinals or 



THE SKELETON. 



43 



lateral ethmoids (Fig. 18), the mesethmoid, and the cribri- 
form plate. The ethmoturbinals are in the form of 
scroll-like laminae which project forward from the trans- 
verse cribriform plate into the nasal cavities. The portion 
which appears externally in the mesal wall of the orbit 




Fig. 16. — Dorsal Aspect of the Cat's Skuee. 
ap, Anterior palatine foramen ; c, canine tooth ; co, coronal suture ; /, for- 
amina in palatine bone, the lateral one is the posterior palatine and 
the mesal one is the sphenopalatine ; fr, frontal ; if, infraorbital fora- 
men; in, interparietal; Ic, lachrymal canal at the anterior border of 
the lachrymal bone; Id, lambdoidal crest; ml, malar; mx, maxillary; 
na, nasal; oc, occipital; p, vertical plate of the palatine; po, post- 
orbital process of the frontal; pm, postorbital process of the malar; 
par, parietal; px, premaxillary ; sq, squamosal part of the temporal; 
sg, sagittal suture ; sp, alisphenoid part of the sphenoid ; tp, temporal 
fossa ; zg, zygomatic process of the squamosal. 



is the os planum. In the recent state, the surfaces of 
these bones within the nasal cavity are covered with a 
mucous membrane over which the first pair of cranial 
nerves (olfactory) are distributed. The delicacy of the 
sense of smell is proportional to the development of the 



44 ELEMENTS OF MAMMALIAN ANATOMY. 

ethmoturbinals. In most orders of animals five scrolls are 
present, but in Echidna there are six and in some Ungu- 
lates there are eight, while in adult Primates there are 
only from one to three, more, however, being present 
in the embryo. 

The mesethmoid is the perpendicular plate of bone 
which, prolonged cephalad by cartilage, separates the 
nasal cavity into two portions. Caudad it is united to 
the cribriform plate, dorsally it articulates with the 
median descending plates of the frontals and the nasals, 
and ventre lly it articulates with the vomer and pre- 
sphenoid. The cribriform plate is the caudal portion 
of the ethmoid (Fig. 18), which, extending transversely 
between the frontals, separates the cranial cavity from 
the nasal cavity. It is pierced by many pinhole foramina 
for the exit of the olfactory nerve. In Ornithorynchus 
(duck-bill of Australia) there is a single large foramen 
in the cribriform plate, as is also the case in birds. 

The temporal is a paired bone lying at the base and 
side of the skull. It contains the organs of hearing. 
It consists of four parts: the squamous or expanded 
portion (Fig. 16), to which the zygomatic process is 
attached; the mastoid (Fig. 17), which is the part caudad 
of the squamosal and dorsal to the bulla; the tympanic, 
which forms the auditory bulla; and the petrous (Figs. 
17 and 18), which contains the internal ear. The 
squamous portion overlaps the parietal dorsally in a 
scale-like manner and is limited ventrally by a clearly 
defined projecting ridge extending above the external 
auditory meatus as the dorsal border of the zygoma. 

The zygomatic process extends cephalad to join the 
zygomatic process of the malar, the two together forming 
the zygomatic arch, or zygoma, to which the masseter 
muscle is attached. Ventral of the root of the zygomatic 



THE SKELETON. 45 

process is the glenoid cavity for the articulation of the 
condyle of the mandible. Immediately caudad of this 
cavity is the postglenoid process. The mastoid portion 
of the bone is somewhat triangular in shape, about two 
centimeters long, and lies caudad of the external meatus. 

The tympanic portion appears on the base of the skull 
as the auditory bulla. Its cavity is divided into two 
unequal chambers by a bony septum rising from the 
floor and reaching almost to the roof. The cephalic 
or true tympanic chamber, sometimes called the middle 
ear, is the smaller, and has on its lateral wall a horseshoe- 
shaped prominence known as the tympanic ring, to 
which the tympanic membrane of the drum of the ear 
is attached. There are four apertures in the walls of 
the cephalic tympanic chamber: The meatus auditorius 
externus, or the external auditory canal; the Eustachian 
tube, leading from the cephalic dorsal angle of the 
chamber to the pharynx; the fenestra ovalis and the 
fenestra rotundum, opening into the internal ear. The 
caudal or mesal chamber of the bulla is larger than the 
cephalic, but has no special features worthy of consider- 
ation. 

The petrous portion of the temporal bone is not visible on 
the external surface of the skull, but may be seen by look- 
ing into the external auditory meatus. It forms the mesal 
wall of the tympanic cavity. The foramen seen in its dorsal 
part is the fenestra ovalis. In a sagittally bisected skull the 
petrous (Fig. 17) may be recognized by the internal audi- 
tory meatus entering it. By removing the bulla, a large 
portion of the petrous bone may be seen from its ventral 
aspect. A central prominence, the promontory, con- 
tains the foramen rotundum opening into the base of 
the cochlea. The apex of the promontory, mesad of 
the fenestra rotundum, forms the wall of the first whorl 



46 ELEMENTS OF MAMMALIAN ANATOMY. 

of the cochlea. Dorsal to the fenestra rotundum is the 
fenestra ovalis, opening into the vestibule of the internal 
ear. In the recent state this opening is closed by a 
membrane in which is imbedded the foot of the stapes. 
The cochlea in the interior of the bone may be displayed 
by cutting away the bony rim of the fenestra rotundum 
and then chipping off a crust of bone in a line from 
this foramen to the juncture of the basioccipital and 
basisphenoid bones. 

The petrous bone, viewed dorsally in a bisected skull, 
appears in the floor of the brain cavity ventrad of the 
tentorium. Its surface is pierced by the internal auditory 
meatus, which gives passage to the auditory nerve. 
Close examination reveals a division of the canal into 
two parts, a ventral for the eighth nerve and a dorsal, 
the aqueductus Fallopii, for the facial nerve. This 
aqueduct twists through the petrous laterad, and thence 
between the petrous, squamosal, and mastoid to the 
stylomastoid foramen. 

The parietal bone is paired and joins its fellow in the 
median line, forming the caudal half of the sagittal 
suture. Its point of greatest convexity is the parietal 
eminence. Its cerebral or internal surface presents 
slight arborescent grooves which in the recent state 
sheltered the meningeal artery. The plate of bone pro- 
jecting obliquely cephalad from the caudal border of 
the parietal is the tentorium, an ossification of the dura 
mater separating the cerebrum from the cerebellum. 

The interparietal is a triangular bone situated at the 
junction of the two parietals and occipital bones. Its 
sutures are usually obliterated quite early. 

The occipital (Figs. 16, 17, and 18) is a single bone 
surrounding the foramen magnum and articulating with 
the interparietal, parietals, temporals, and sphenoid. In 



±-:g. 17. — Vents litory 

basioccdpital ; c, can 
of t] nal auditory meatus; 

efc, opening at the Eustach foramen mag- 

num ; gc, gle:. . hamular pro- 

jrbital foramen ; in, 
.Jar foramen; Id, lambdoidal rid e xiila; ml, 

mc mastoid portion of the tem- 

poral ; /?: foramen 

post- 
-s; pr, pr^ 
rotundir 

mastoid fora forax or foramen laceru: 

ruling the septurr 
?f squam 



THE SKELETON. 



47 



the young kitten it is composed of four parts : the supra- 
occipital, lying dorsal to the foramen magnum, the two 




?+*¥"* 



Fig. 17. 



exoccipitals , lying laterad of it, and a basioccipital, 
bounding it ventrally. The crescentic elevation on the 



48 ELEMENTS OF MAMMALIAN ANATOMY. 

supraoccipital near its parietal margin is the lambdoidal 

ridge t to which the cephalohumeral muscle is attached 
(Fig. 48). 

The exoccipitals bound the cerebellum laterally and 
support the occipital condyles, which articulate with the 
atlas or first vertebra. Immediately caudad of the bulla 
is the paroccipital process. There are two foramina. 
one of which, the anterior condyloid, opens vent rally 
with the jugular foramen adjacent to the bulla, while 
the other, the posterior condyloid, opens more dor sally 
at the side of the condyle. The former transmits the 
twelfth hypoglossal) cranial nerve, supplying the larynx, 
hyoid bone, and tongue. The jugular foramen, or 
foramen lacerum posterius, is at the juncture of the 
bulla, exoccipital. and basioccipital. The internal jugular 
vein and the ninth, tenth, and eleventh nerves pass 
through it. The basioccipital portion of this bone lies 
entirely on the ventral aspect of the skull. It articu- 
lates cephalad with the basisphenoid by a suture which 
is generally obliterated in cats three or four years old. 

The sphenoid bone lies in the center of the base of the 
skull. It is composed of eight parts, corresponding to 
eight distinct bones in the lower vertebrates: the bast- 
sphenoid, articulating caudad with the basioccipital; 
two alisphenoids, extending dorsad from the basisphenoid 
and articulating caudad with the temporals (Figs. 17 
and 18 ); two pterygoids, projecting ventrally from the 
basisphenoid and terminating in sharp processes; a 
presphenoid in the midventral line cephalad of the 
basisphenoid; two orbitosphenoids, extending dorso-later- 
ally from the presphenoid and articulating cephalad with 
the frontals. In an old cat, the sutures between these 
eight' parts become more or less obliterated. The basi- 
sphenoid together with the alisphenoids is sometimes 



THE SKELETON. 



49 



called the posterior sphenoid in distinction to the anterior 
sphenoid, composed of the presphenoid and orbito- 
sphenoids. 



TABLE OF THE FORAMINA OF THE SKULL. 



Foramina. 


Bones Surrounding the 
Foramina. 


Structures Traversing the Fora- 
mina. 


Infraorbital. 


Superior maxillary. 


Infraorbital nerve of the supe- 
rior maxillary division of the 
fifth. 


Anterior palatine. 


Maxillary and pre- 


Nasopalatine branch of the 




maxillary. 


fifth cranial nerve and nasal 
artery. 


Sphenopalatine. 


Palatine. 


Sphenopalatine nerve and 
sphenopalatine artery. 


Posterior palatine. 


Palatine. 


Palatine nerve and artery. 


Olfactory foramina. 


Ethmoid. 


Olfactory nerve. 


Optic. 


Orbitosphenoid. 


Optic nerve and meningeal 
artery. 


Lacerum anterius, 


Alisphenoid and 


Third, fourth, and sixth cranial 


or sphenoidal fis- 


orbitosphenoid. 


nerves and first division of 


sure. 




fifth cranial nerve. 


Rotundum. 


Alisphenoid. 


Second division of fifth cranial 
nerve. 


Ovale. 


Alisphenoid. 


Third division of fifth cranial 
nerve. 


Lacerum medium. 


Petrous and basi- 

sphenoid. 
Petrous. 


Internal carotid artery. 


Internal auditory 


Eighth cranial nerve. 


meatus. 






Aqueduct of Fallo- 


Petrous, mastoid, 


Seventh cranial nerve. 


pius. 


and tympanic. 




Stylomastoid. 


Tympanic and mas- 
toid. 


Seventh cranial nerve. 


Jugular or posterior 


Occipital and tem- 


Ninth, tenth, and eleventh 


lacerated. 


poral. 


cranial nerves and jugular 


Anterior condyloid. 


Exoccipital. 


vein. 
Twelfth cranial nerve. 



The basisphenoid presents on its dorsal or cerebral 
surface the sella turcica, or pituitary fossa, which lodges 
the pituitary body of the brain (Big. 90). The posterior 
boundary of this fossa is the clinoid plate, and its lateral 
projections are the posterior clinoid processes. On each 
side of the basisphenoid there extends dorsally in a 



ELEMENTS OF MAMMALIAN ANATOMY 



narrow strip to the parietal the alisphenoid. at the base 
of which, eephalad of the auditory bulla, are three 
foramina in a line. The most cephalic and largest one 




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is the sphenoidal fissure, or anterior lacerated foramen, 
which transmits the third, fourth, and sixth cranial 
nerves supplying the eyeball muscles, and the first 



THE SKELETON. 5 1 

branch of the fifth nerve. This foramen is between the 
alisphenoid and the orbitosphenoid. The other two 
foramina, rotundum and ovale, transmit the second and 
third divisions of the fifth nerve. 

The pterygoid portion of the sphenoid is a paired bone 
(Figs. 17 and 18) lying on either side of the cephalic 
half of the basisphenoid and the caudal half of the 
presphenoid. In the adult cat the sutures are some- 
times obliterated so that this bone appears as a caudal 
continuation of the palatine. The two pterygoid bones 
or plates form the descending walls, and, together with 
the median portion of the sphenoid, the roof of the 
mesopterygoid fossa, whose cephalic continuation is the 
posterior nares. From the ventral posterior angle of 
each projects the hamular process, dorsal of which is 
seen the small external pterygoid process. Between the 
bases of the hamular and the external pterygoid processes 
is the small external pterygoid fossa. 

The presphenoid bone is the narrow median bone ex- 
tending from the basisphenoid to the vomer. It contains 
within it two large sinuses into which project the ventral 
scrolls of the ethmoturbinal bones. The alisphenoids 
enter into the formation of the mesal walls of the orbits 
and are perforated at their bases by the optic foramina, 
through which pass the optic nerves. 



fr\ BONES OF THE FACE. 

There are seven paired bones in the face and two 
single ones, making in all sixteen. 

The premaxillary, with its fellow, extends ventrad and 
laterad of the anterior nares. These bones bear the six 
incisor teeth. The anterior palatine or incisor foramina 
connect the oral cavity with that of the anterior nares. 



52 ELEMENTS OF MAMMALIAN ANATOMY. 

In life, these foramina transmit the naso-palatine nerves. 
In the Primates, the premaxillary is anchylosed to the 
maxillary although it arises from a separate center of 
ossification. 

The maxillary is a paired bone which meets its fellow 
in the median line in the roof of the mouth. All its 
articulations are visible externally except those with the 
maxilloturbinal, ethmoid, and vomer. Five teeth, a 
canine, three premolars, and a molar, are present in this 
bone of the adult cat. The molar is wanting to the 
young. The several portions of the bone are as follows: 
the palatine plate, appearing in the roof of the mouth; 
the nasal process, extending dorso-caudad to the frontal; 
the malar process, extending ventrad to the orbit to 
articulate with the malar bone; and the orbital plate, 
which is the root of the malar process, forming a partial 
floor to the orbital cavity. The large foramen leading 
from the orbital cavity through the orbital plate is the 
infraorbital foramen for the passage of the infraorbital 
branch of the superior maxillary branch of the fifth 
nerve. 

The palatine bone with its fellow helps to form the 
roof of the oral cavity and the floor of the nasal cavity. 
It is composed of two plates: one, vertical, forming the 
lateral walls of the posterior nares and the cephalic part 
of the walls of the median pterygoid fossa, and a portion 
of the nasal wall of the orbital cavity; the other, hori- 
zontal, forming part of the roof of the mouth. The ver- 
tical plate is pierced by two foramina, the posterior pala- 
tine and the sphenopalatine, each of which transmits a 
palatine nerve and artery (Fig. 16). 

The vomer is a single narrow bone which in the nasal 
cavity articulates dorsally with the mesethmoid and 
ventrally with the palatines and the palatine plates of 



THE SKELETON. 53 

the maxillary, in the median line. This bone, with the 
mesethmoid and its cartilage, forms the nasal septum, 
dividing the nasal cavity into two chambers. It is best 
demonstrated by removing the palatines, when it may 
be seen extending cephalad from its bifurcated articula- 
tion with the presphenoid to its articulation with the 
premaxillaries. The caudal portion of the bone is ex- 
panded horizontally and articulates with the ventral eth- 
moturbinals. Its dorsal margin is bifurcated for articu- 
lation with the mesethmoid. 

The maxilloturbinal is a paired bone occupying the 
anterior portion of the nasal cavity (Fig. 18). It is com- 
posed of a few scrolls which, when the nasal bone is 
removed, may be seen attached to the maxillary. It 
consists of a horizontal longitudinal plate, whose lateral 
border is fixed to the maxillary while the mesal border 
bifurcates into a dorsal curved plate and a ventral scroll. 
The space between the maxilloturbinal and cephalic por- 
tion of the lateral ethmoid is the middle nasal meatus. 
The maxilloturbinal bone in man receives the name of 
the inferior turbinated, in distinction to the middle and 
superior turbinated bones, constituting the lateral eth- 
moid. 

The nasal bone, joining with its fellow in the median 
line, forms a large part of the roof of the nasal chamber. 
It articulates with the premaxillary, maxillary, and 
frontal on the surface, and the ethmoid within the nasal 
chamber. 

The lachrymal bones are two in number and lie in the 
cephalic part of the nasal walls of the orbits. Each 
articulates with the maxillary, frontal, os planum of 
the ethmoid, and the malar. The bone has about half 
of the area of the finger-nail. The lachrymal canal is 
bounded by the lachrymal and the maxilla. This canal, 



54 



ELEMENTS OF MAMMALIAN ANATOMY. 



beginning in a vertical groove, the lachrymal groove, car- 
ries the duct permitting the tears to pass from the eye 
into the nasal chamber (Fig. 16). 

The malar bone is paired. It forms the cheek as well 
as the lateral and cephalic border of the orbit. The arch 
largely formed by this bone is the zygoma. The process 
projecting dorsad toward the postorbital process of the 
frontal bone is the postorbital process of the malar. The 
masseter muscle originates on the border of the malar. 



c ™ Prm. mol 

dl . / 





mf.d.fm. ^ 

Fig. 19. — Mesal or Inner Aspect oe the Mandible. 
ang, Angle; cndyl, condyle; cor pr, coronoid process; can, canine tooth; 
inc, incisor teeth; inf. d. ftn, inferior dental foramen; in, inferior 
notch ; mol, molar tooth ; prm, premolar teeth ; dt, diastema ; sm, sur- 
face of symphysis ; up, superior notch. 



The mandible or inferior maxillary is the single bone 
forming the lower jaw (Figs. 17 and 21). It is made up 
of two halves which are united by an immovable articula- 
tion or symphysis (Fig. 19) at the chin. Each half con- 
sists of a horizontal and an ascending ramus. On its 
alveolar border the horizontal ramus bears three incisor 
teeth, a canine, two premolars, and a molar tooth. In 
the caudal part of the oral surface of this ramus is the in- 



THE SKELETON. 



55 




eh 



ferior dental foramen, which transmits the inferior dental 
nerve and artery traversing the dental canal extending 
within the bone to the mental foramen on the lateral sur- 
face near the base of the canine tooth. The space on the 
dorsal border between the canine 
and the first premolar tooth is 
called the diastema. 

The ascending ramus or por- 
tion of the bone caudad of the 
inferior tooth is marked by six 
features: (i) the fossa on the 
outer or lateral surface which 
gives insertion to the masseter 
muscle ; (2 ) the angle which is the 
caudoventral termination of the y 

bone; (3) the inferior notch im- 
mediately dorsal of the angle ; (4) 
the condyle for the articulation 
with the glenoid cavity of the 
temporal; (5) the superior notch 
dorsal of the condyle; (6) the 
coronoid process, which is the 
dorsal termination of the ascend- 
ing ramus and gives insertion to 
the temporal muscle. 



bh\ 



' ; ch 

, 'sh 






Id 



cr 



*? 



Fig. 20.— Ventral Aspect 
of Larynx, Hyoid Bones, 
and Tongue. The tongue 
has been cut transversely 
near its middle and its mus- 
cles fixing it to the hyoid 
have been removed. 

bh, Basihyal; ch, ceratohyal; 
cr, cricoid cartilage of the 
larynx; eh, epihyal; ep, 
epiglottis; Ig, cricothyroid 
ligament ; lyh, thyrohyal ; 
rg, rings of cartilage in the 
trachea; tc, thyroid cartil- 
age of the larynx ; tm, tym- 
panohyal; sh, stylohyal. 



THE HYOID BONES OR HYOID 
APPARATUS. 

The hyoid bones consist of two 
jointed rods, one on either side 

(Figs. 20 and 21), hanging from the temporal bone, and 
supporting the larynx. Each rod is composed of six 
parts : the epihyal ; the ceratohyal ; the tympanohyal ; the 



56 ELEMENTS OF MAMMALIAN ANATOMY. 

basihyal ; and the thyrohyal. The dorsal end of the thyro- 
hyal is prolonged by a piece of cartilage, the chondrohyal. 
The hyoid apparatus varies greatly among mammals. 
In man it consists of a single bone composed of the body 
or basihyal, two small cornua representing the cerato- 
hyals, and two large cornua representing the thyrohyals. 
The bone is suspended from the skull by ligaments cor- 
responding to the bony chain in the cat. 



PRACTICAL QUESTIONS AND SUGGESTIONS. 

1. How many more bones present in the cat than in man? 

2. In what two parts of the skeleton does the number of bones in 
the cat exceed those in man? 

3. What is a sesamoid bone? 

4. Find on a specimen a sesamoid bone and describe it. 

5. Draw a lateral aspect of the skull and label all parts 

6. What are the paired bones of the cranium? 

7. Name the single bones of the face. 

8. Draw the caudal aspect of the skull and label all parts. 

9. Which bones of the skull derive their names from their location? 

10. Which bones of the skull are pierced by more than two foramina? 

11. Write a description of the orbital cavity. 

12. Which foramina of the skull derive their names from their shape 
or size? 

13. Which foramina derive their names from their location? 

14. Which foramina transmit important blood-vessels? 

15. Draw figures representing relative shapes and sizes of all foramina 
of the skull. 

16. What bones enter into the formation of the brain cavity? 

17. Write about 200 words describing the nasal cavity. 

18. Draw a ventro-lateral aspect of the auditory bulla and label all 
features. 

19. Write a description of the auditory bulla and name some mam- 
mals in which it is absent. 

20. Which bones of the skull are composed of more parts in the young 
than in the adult? 

21. Name the principal sutures of the skull. 

22. Name the parts of the sphenoid bone in the order of size. 

23. Name the bones of the skull visible from the dorsal aspect. 

24. Name the bones of the skull visible from the cephalic aspect. 

25. What bone of cranium paired in the cat is single in man? 



THE SKELETON. 



57 



26. What bone present in face of the cat is wanting as a separate ele- 
ment in man? 

27. Draw lateral aspect of mandible and label all features. 

28. Name the bones bearing the teeth. 

29. Name the elements of hyoid apparatus in order. 

30. Draw a section of the frontal bone showing diploe. 

3 1 . Describe the difference between the relative locations of the cranial 
and facial portions of the skull in cat and man. 

32. Name five membrane bones and five cartilage bones. 



VERTEBRAE. 

The vertebral column is composed of the following five 
groups of vertebrae: seven cervical, thirteen thoracic, 
seven lumbar, three sacral, and caudal varying from 
four to twenty-six. The following six features are com- 
mon to all of the vertebrae in the first four groups except 
the atlas: (i) the body of the vertebra (Fig. 22), which 
forms the floor of the neural canal and articulates with 
the adjacent vertebrae by means of interposed discs of 
cartilage; (2) the transverse processes, which project 
laterad from the body or from the walls of the neural 
canal; (3) a spinous process, which projects dorsad from 
the roof of the neural canal; (4) the neural arch, com- 
posed of a pedicle on either side, forming the ventro- 
lateral walls of the neural canal, and the laminae, extend- 
ing dorsad from the pedicles to complete the dorsal wall 
of the neural canal; (5) the intervertebral notch, which, 
with the notch of the succeeding vertebra, forms the 
intervertebral foramen for the exit of a spinal nerve; (6) 
the articular processes or zygapophyses, two of which pro- 
ject cephalad and two caudad from each vertebra. The 
former are called the anterior zygapophyses, and the 
latter posterior zygapophyses. 

The first cervical vertebra, or atlas, is characterized by 
its large horizontally expanded transverse processes, the 
5 



58 



ELEMENTS OF MAMMALIAN ANATOMY. 



absence of a spinous process, and its rudimentary body. 
Its true body in the embryo, becomes united to the axis 




as the odontoid process. The cephalic margin of the 
neural arch is prolonged at each side into a process or 



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THE SKELETON. 



59 




Fig. 22.— Plan of a Ver- 
tebra. 

sp, Spinous process; ar, 
articular process ; ns, 
transverse process; nc, 
neural canal; pd, pedi- 
cle ; lm, lamina ; en, cen- 
trum or body. 



articulation with the occipital condyles (Fig. 17) of the 
skull. The root of this articular process is pierced by a 
foramen giving passage to the first 
spinal nerve and the vertebral ar- 
tery and vein (Fig. 23, }r). From 
the lateral opening of this foramen 
(/r) a groove is continued ventrad 
to the middle of the transverse pro- 
cess, where it leads into the longi- 
tudinal vertebrarterial canal com- 
mon to the first six cervical verte- 
brae. The vertebral artery and vein 
course through this canal (Fig. 23). 
The axis, or second vertebra, is 
characterized by its odontoid pro- 
cess, which projects within the at- 
las, and also by its elongated spi- 
nous process, which projects both cephalad and caudad. 

The transverse process projects 
caudad from the body, which is 
flattened dorsoventrally. This 
process is pierced at its base by 
the vertebrarterial canal. 

The remaining five cervicals 
are very similar to one another. 
The seventh has no vertebrar- 
terial canal. The spinous pro- 
cesses grow successively longer 
from . the third to the seventh 
(Fig. 21). The transverse pro- 
cesses of the fourth and fifth are 
bifurcated, the dorsal branch be- 
ing called the transverse element 
and the ventral one the costal element, since it is really the 




Fig. 23. — Dorsocaudae As- 
pect of Atlas. 

tr, Transverse process; nc, 
neural canal; sp, spinous 
process ; fr, aperture of the 
transverse part of the ver- 
tebrarterial canal which 
enters the atlas at vf; azg, 
anterior zygapophysis ; zg, 
posterior zygapophysis. 




60 ELEMENTS OF MAMMALIAN ANATOMY. 

rudiment of a rib. The transverse process of the fifth ends 

nl sp 



-oi.pt 



Fig. 24. — Lateral Aspect of the Axis. 
ar st, Anterior zygapophyses ; od pr, odontoid process; nl sp, neural spine 
or spinous process ; p zg, posterior zygapophysis ; trs pr, transverse 
process; irt c, vertebrarterial canal. 

in three branches. The following features are common to 

all thirteen thoracic vertebra? : a 
spinous process, projecting from 
the dorsum of the neural arch ; 
two cephalic articular processes or 
anterior zygapophyses, facing 
dorsad or dorsolaterad ; two cau- 
dal articular processes or posterior 
zygapophyses, facing ventrad or 
ventromesad; a body whose 
transverse diameter is greater 
i'-Ii than the vertical diameter; and 
transverse processes. There are 
two half facets on each side of 
the body of every thoracic verte- 
bra except the first, eleventh, 
twelfth, and thirteenth. The 
head of a rib thus articulates 
with two vertebrae ("Fig. 28). 
The body of the first vertebra 

bears on each side a whole facet and a half facet. The 




ce n 

Fig. 2.5. — Laterocaudal 
Aspect of the Second 
Thoracic Vertebra. 

/ r, Transverse process ; nc, 
neural canal; ce, facet for 
tubercle of rib: ar, poste- 
rior zygapophysis; s, spi- 
nous process; c, centrum; 
n, intervertebral notch; e, 
pedicle; /, lamina. 



THE SKELETON. 



6l 



eleventh, twelfth, and thirteenth bear a whole facet on 
each side of the body. 

The transverse processes of the first eleven bear facets 
for the articulation with the tubercles (Fig. 25) of the 
ribs. The last three thoracic vertebrae are characterized 
by mammillary processes springing from the dorsolateral 
portion of the roots of the anterior zygapophyses. 




Fig.. 26. — Caudal Aspect of 
Fourth Lumbar Vertebra. 

a, Accessory process; cr, centrum 
or body; pa, pedicle; tr, trans- 
verse process ; s, neural canal ; sp, 
spinous process ; zg, the mammil- 
lary process of the anterior zyga- 
pophysis ; am, lamina ; pz, poste- 
rior zygapophysis. 



Fig. 27, — Dorsal Aspect of the 
Sacrum. 

fl, Floor of the neural canal ; fr, dor- 
sal aperture of the intervertebral 
foramen; It, lateral mass; pzg, 
posterior zygapophysis; sp, spi- 
nous process ; si, auricular surface 
for articulation with the ilium ; tr, 
transverse process; zgt, tubercle 
formed by fusion of the zygapoph- 
yses ; zg, anterior zygapophysis. 



The following features are common to all of the lumbar 
vertebra: & spinous process projecting dorsocephalad 
(Fig. 26) ; a transverse process projecting ventrocephalad 
on either side from the body; anterior zygapophyses and 
posterior zygapophyses. A mammillary process or meta- 
pophysis is present on the root of the anterior zygapoph- 



62 ELEMENTS OF MAMMALIAN ANATOMY. 

\ Ms of the first five bones, and an accessory process or 
anapophysis occurs on the caudal margin of the wall of 
the neural arch of all except the last vertebra. The 
transverse processes increase in length and curvature 
caudally. The spinous processes increase in length in 
the same order, and the neural canal likewise enlarges 
caudally. 

The sacrum is a single bone (Fig. 27) formed by the 
union of three sacral vertebrae. The limit of each element 
is marked by the dorsal and ventral intervertebral fora- 
mina which furnish passage for the dorsal and ventral 
branches of the spinal nerves. The two tubercles on 
either side of each of the three median spinous processes 
are the result of the fusion of the articular processes. 
The cephalic portion of the bone presents on its lateral 
aspect the auricular surfaces for articulation with the 
ilium. This expansion appears to be a modified transverse 
process. Prominent transverse processes also project from 
the caudal angles. 

The caudal vertebrae vary greatly in number. Accord- 
ing to Mivart, there are only four in the Manx cat; and 
according to Jayne, there may be as many as twenty-six 
in some varieties of the common cat. The transverse 
processes and zygapophyses become less prominent from 
the third vertebra to the eighth or ninth, where they are 
present only as slight ridges. The spinous process is 
present in the first three, but dwindles to a ridge in the 
fourth. The first six or seven elements possess a neural 
arch which more distally loses its roof, making the neural 
canal a mere groove. The groove becomes fainter dis- 
tally and finally disappears entirely. The chevron bones 
are the paired ossicles projecting ventrad from the 
cephalic ends of the bodies of the vertebrae, from the 
second or third to the thirteenth vertebra. In the sixth, 



THE SKELETON. 63 

seventh, and eighth vertebrae the chevron bones unite 
ventrally in the middle line, forming an arch. The last 
ten caudal vertebrae are scarcely more than cylinders of 
bone representing the bodies of the vertebrae. 

The number of vertebrae in the different species of 
mammals varies widely. As a rule, there are seven 
elements in the cervical region. The sea cow (Manatus) 
has only six cervical vertebrae, while the three-toed sloth 
has nine. The number of thoracico-lumbar varies from 
sixteen in the orang to thirty-six in the cetacean Del- 
phinus. The elements composing the sacrum likewise 
vary from one in the ape, Cercopithecus, to nine in some 
of the Edentata. The human sacrum is composed of 
from four to six vertebrae. The same is true of the 
gorilla, chimpanzee, and orang. The caudal vertebrae 
vary greatly in number in the different forms. In the 
adult human there are present only four or five vertebrae, 
which form a single bone, the coccyx, while in the embryo 
eight segments make up the caudal region. Ossification 
takes place, however, in only five or six segments. 



THE STERNUM. 

The sternum of the cat is composed of eight pieces, 
called sternebrae, which lie in the median line on the 
ventral side of the chest (Fig. 21). The sternum serves 
for the attachment of the cartilaginous portions of nine 
pairs of ribs. The first sternebra (Fig. 28), which ends 
cephalad in a laterally compressed pointed process, is the 
manubrium.' The six succeeding sternebrae form the body 
or gladiolus ; the caudal piece is called the ensiform or 
xiphoid process. It is terminated by a flat piece of carti- 
lage. The cartilaginous portion of the first rib articulates 
with the manubrium near its middle. The ribs from the 



64 



ELEMENTS OF MAMMALIAN ANATOMY. 




Fig. 28. — Ventral Aspect of the Bones of the Thorax. The num- 
bers on the vertebral or bony portions of the ribs indicate the names 
of the ribs. The numbers of the last four ribs are placed just ceph- 
alad of them. 

c, Cartilaginous part of first rib ; cr, cartilaginous disc between the bodies 
of the vertebrae; en, ensiform process; hd, heads or capitula of ribs; 
m, manubrium ; mr, attachment of twelfth to the eleventh rib ; n, free 
termination of thirteenth rib; r, attachment of the eleventh to the 
tenth rib ; tb, tubercle of first rib ; in, transverse process of first thoracic 
vertebra; v, body of vertebra. 



THE SKELETON. 



65 



second to the seventh inclusive are attached at the 
junctions of the sternebrae. The eighth and ninth ribs 
are attached near together on the caudal end of the 
seventh sternebra. 



RIBS. 

There are thirteen pairs of ribs in the cat. The nine 
cephalic are called true ribs because they articulate dor- 
sally with the spinal column and ventrally with the 
sternum. The other four (Fig. 28) are 
false ribs, three of which articulate 
ventrally with other ribs, while the 
fourth has no ventral articulation, and 
is therefore called a floating rib. Each 
rib is composed of two parts, the ver- 
tebral or bony portion and the sternal 
or cartilaginous. 

The following description of the 
sixth will serve to give a correct idea 
in general of the anatomy of a rib. 
Its vertebral portion (Fig. 29) presents 
four features: a head or capitulum, 
which articulates with the bodies of 
the fifth and sixth thoracic vertebrae ; 
a tubercle, which articulates with the 
transverse process of the sixth thor- 
acic vertebra ; a neck, which is the con- 
stricted portion between the capitu- 
lum and tubercle ; and the shaft, in- 
cluding the portion of the rib between 
the tubercle and its articulation with 
the sternal or cartilaginous portion. The bend in the shaft 
beyond the tubercle is the angle. The sternal portion of 
the rib, consisting of cartilage, is sometimes called the cos- 




Fig. 29.— Caudal As- 
pect of Sixth Rib. 

ag, Angle; cr, pit for 
articulation with 
cartilaginous por- 
tion ; h, capitulum ; 
nk, neck; sh, shaft; 
tb, tubercle with fa- 
cet for articulation 
with transverse pro- 
cess. 



66 ELEMENTS OF MAMMALIAN ANATOMY. 

tal rib. In the sixth rib the costal portion is about half as 
long as the vertebral portion. 

Certain ribs present marked features varying from the 
sixth. The first rib is stout and flat and has no distinct 
angle. The articular surface of its head is not divided 
into two facets, as is the case in all the others except 
the three caudal ones. The lengths of the ribs increase 
from the first to the ninth. The last three ribs have no 
necks and no tubercles for articulation with the transverse 
processes of the vertebrae. 

The number of ribs varies from nine pairs in the 
cetacean Hyperoodon to twenty-four in the two-toed 
sloth (Choloepus). In most fishes and snakes, ribs are 
present throughout both the trunk and tail regions, but 
with the assumption of life on land, and the development 
of limbs, the vertebrates have suffered a degeneration of 
the ribs in all parts except the middle portion of the 
trunk. In the embryo, however, anlage of ribs occurs 
in all regions of the trunk, but they early coalesce with 
the vertebrae except in the thorax. 



PRACTICAL QUESTIONS AND SUGGESTIONS. 

1. Draw caudal aspect of third thoracic vertebra and label all features. 

2. Describe the differences between the first and last thoracic ver- 
tebrae. 

3. What feature common to all thoracic vertebrae not present on any 
of the other vertebrae? 

4. Draw the caudal aspect of the fourth cervical vertebra. 

5. What feature common to all cervical vertebrae except seventh 
but not present in any other vertebrae? 

6. Draw cephalic aspect of atlas and label all features. 

7. Compare the third and seventh cervical vertebrae. 

8. What two features serve to distinguish the lumbar from all other 
vertebrae? 

9. Draw the cephalic aspect of the second lumbar vertebra and label 
all features. 

10. Wherein does the seventh lumbar vertebra differ from the first? 



THE SKELETON. 67 

11. How do you distinguish the caudal from the cephalic aspect of 
any vertebra? 

12. Draw ventral aspect of sacrum and label all features. 

13. Give the two features distinguishing the caudal vertebrae from 
all others. 

14. Note the size and direction of the spinous process throughout 
the column. 

15. Describe the variation in number of the different groups of ver- 
tebrae in other mammals. 

16. Draw lateral aspect of sternum and label all features. 

17. Describe the attachment of ribs to sternum. 

18. What features common to all the ribs? 

19. Name ribs having a tubercle. 

20. Draw first rib and label all features. 

21. Draw cephalic aspect of ninth rib and label all features. 

22. How do you distinguish a false rib from a true rib? 

23. What features mark the caudal aspect of a rib? 

24. Make a drawing showing the articulation of a rib with the spinal 
column and label all parts. 

25. How do ribs vary as to number in mammals? 



THE THORACIC LIMB. 

The thoracic or fore-limb of the cat is composed of a 
scapula, clavicle, humerus, ulna, radius, seven carpals, 
five metacarpals, and fourteen phalanges (Fig. 20). The 
scapula and clavicle form the shoulder girdle. 

The scapula, commonly called the shoulder-blade (Fig. 
30), is not articulated with the bones of the trunk, but 
is held in position by the serratus magnus, levator anguli 
scapulae, and other less important muscles. It articulates 
with the head of the humerus by the glenoid cavity. It 
presents three well-marked borders: the cephalic or an- 
terior, the vertebral, and the axillary adjacent to the 
vertebrae on the side near the axilla or armpit. The 
outer surface of this bone is divided by a strong spine 
into two nearly equal fossae, the cephalic of which is the 
supraspinous, and the caudal one the infraspinous, fossa. 



68 



ELEMENTS OF MAMMALIAN ANATOMY. 



From the lower part of the spine project the acromion 
and metacromion processes. The subscapular fossa occu- 
pies the entire inner or mesal surface. 




rr\ 



r «ft-. 



^Afij M 



¥ 



Fig. 30. — Lateral or Outer Aspect op the Scapula. 
ac, Acromion process ; ax, axillary border ; c, coracoid process ; gl, glenoid 
cavity; m, metacromion process; sc, suprascapular notch; sp, spine; 
sup. fos, supraspinous fossa ; vr, vertebral border ; n, neck. 



A slight constriction between the base of the spine and 
the margin of the glenoid cavity is termed the neck. 
From the cephalic side of the latter the coracoid process 

curves mesad. 

The clavicle is a slender 
curved bone, about one inch 
long, imbedded in the mus- 
cle between the manubrium 
and the coracoid process 
(Fig. 21). It does not ar- 
ticulate with any bone, but 
is held in place by the cephalohumeral and cleidomastoid 
muscles (Fig. 48). 

The shoulder girdle varies somewhat among the Mam- 




Fig. 31 



Caudal Aspect of Left 
Clavicle. 
b, Mesal end ; a, lateral end. 



THE SKELETON. 



malia. The clavicle is never fully developed in any of 
the Carnivora . Primates , Chiroptera , 
Edentata, and Monotremata are the 
only orders in which all the species 
possess clavicles. A third element of 
the shoulder girdle, known as the cora- 
coid, is a fully developed bone only in 
the Monotremata, where it articulates 
at one end with the scapula, forming 
part of the glenoid cavity, and at the 
other end with the presternum. In 
the other mammals the coracoid is 
represented by the coracoid process 
of the scapula, which ossifies from a 
separate center. In many of the lower 
vertebrates a distinct coracoid is pres- 
ent. 

The humerus is the bone of the arm 
or brachium. It articulates proxi- 
mally with the glenoid cavity of the 
scapula (Fig. 2 1 ) and distally with the 
ulna and radius. It consists of three 
parts : the proximal extremity bearing 
the head, the middle portion or shaft, 
and the distal extremity (Fig. 32). The 
greater and lesser tuberosities separated 
by the bicipital groove lodging the 
tendon of the biceps muscle, are the 
two processes on the proximal ex- 
tremity. The former is the larger 
and more cephalic, and serves for the 
insertion of the supraspinatus muscle 
(Fig. 49). The distal extremity is marked by two im 
portant projections, the external and internal condyles 




It 

Fig. 32. — Cephauc 
Aspect of Right 
Humerus. 

bl, Bicipital groove ; cr, 
supra condyloid 
ridge ; cp, capitellum 
for articulation with 
the radius; dr, del- 
toid ridge; et, ex- 
ternal condyle ; gf, 
greater tuberosity ; 
it, internal condyle; 
//, lesser tuberosity; 
sp, supracondyloid 
foramen or entepi- 
condylar foramen ; 
sr, supinator ridge ; 
tr, trochlea for ar- 
ticulation with ulna. 



7° 



ELEMENTS OF MAMMALIAN ANATOMY. 



Extending proximad from the external condyle is the 
supinator ridge. Proximad of the internal condyle is 
the supracondyloid foramen transmit- 
ting the mediannerve and brachial artery 
(Figs. 72 and 89). The olecranon fossa 
is the deep cavity on the caudal aspect 
of the bone, opposite the coronoid fossa. 
The articular surface of the distal ex- 
tremity consists of the capitellum, for ar- 
ticulation with the head of the radius, 
and the trochlea, for articulation with the 
sigmoid cavity of the ulna. On the 
cephalic side of the proximal third of 
the bone is the rough deltoid ridge for the 
insertion of the deltoid muscle which 
arises from the shoulder girdle. 

The ulna is the longest bone of the 
forearm, or antebrachium, and is caudad 
of the radius. It articulates in the greater 
sigmoid cavity with the trochlea of the 
humerus and in the lesser sigmoid cavity 
with the head of the radius. The distal 
articulation is with the radius, cuneiform 
and pisiform (Fig. 21). The olecranon 
process forms the proximal termination 
of the bone and serves for the insertion 
of the triceps muscle. Distad of the sig- 
moid cavity is a projection known as the 
coronoid process. The styloid process 
forms a small projection on the distal 
extremity of the bone. 

The radius is the preaxial or cephalic 
bone of the antebrachium. It articulates proximally with 
the capitellum of the humerus and the lesser sigmoid cavity 



Fig. 33. — Lateral 
or Outer As- 
pect of the 
Right Ulna. 

ar, Articular facet 
for radius ; cr, 
coronoid process ; 
gs, greater sig- 
moid cavity; Is, 
lesser sigmoid 
cavity; on, olec- 
ranon process ; 
st, styloid pro- 
cess. 



THE SKELETON. 



71 



of the ulna, and distally with the scapholunar and radius 
It bears but two processes, the tubercle and the styloid pro 
cess. The tubercle (Fig. 34) is a slight 
knot near the proximal end on the ulnar 
side. Proximal from the tubercle is the 
neck which supports the head bearing a 
concave crown for articulation with the 
capitellum of the humerus. The styloid 
process projects from the distal end par- 
allel with the process of the same name 
on the ulna. 

The bones of the antebrachium in 
many mammals are more or less coal- 
esced. In the Chiroptera and many of 
the Ungulates the radius is enlarged at 
the expense of the ulna, whose proximal 
third only remains. The primitive Un- 
gulates of the lower tertiary period pos- 
sessed a complete ulna as well as radius. 
The phylogeny of the horse's limb illus- 
trates the gradual development of the 
antebrachium of the Kquidae (Fig. 35). 
Fossil remains reveal the fact that mam- 
mals existed as early as the triassic pe- 
riod, when the sedimentary rock forming 
the triassic strata was laid down. This 
probably occurred 10,000,000 years ago. 

According to palaeontological investi- 
gations, the Ungulata arose from the 
Condylarthra, a group of small five- toed 
mammals of the lower Eocene, best rep- 
resented by the typical genus Phenaco- 
■dus. In this genus and its successor, Hyracotherium, the 
ulna and radius are well developed and distinct. Orohip- 




Fig. 34. — Mesal 

or Inner As- 
pect of Right 
Radius. 
fc, Articulatory sur- 
face for capitel- 
lum of humerus; 
hd, head, — the 
point of the ar- 
row is on the ar- 
ticulating surface 
for the lesser sig- 
moid cavity; nk, 
neck; sc, articu- 
latory surface for 
scapholunar ; st, 
styloid process ; 
tb, tubercle ; ul, 
facet for ulna. 



r- 



ELEMENTS OF MAMMALIAN ANATOMY. 



pus, the descendant of Hyracotherium, also shows a dis- 
tinct radius and ulna, but in the later forms of the horse 
line the ulna gradually diminishes in size and becomes 




Kit, 




TUC 





z t\ 4 

3 

Fig. 35. — (See opposite page for explanation.) 

more and more coalesced with the radius, until in Equus 
scarcely more than the proximal third remains (Fig. 37). 
Carpus. — The carpus consists of seven bones arranged 



THE SKELETON. 



73 



in two rows (Fig. 36). Beginning on the pollex side, the 
scapholunar, cuneiform, and pisiform compose the proxi- 



H 



A L 






Fig. 35. — Genealogy of the Horse. 
F, Forefoot; H, hindfoot; A, forearm; L, leg; /, Orohippus or Pachyno- 
lophus; II, Mesohippus; III, Miohippus; IV, Protohippus ; V, Plio- 
hippus; VI, Equus; 2, 3, 4, and 5 are the second, third, fourth, and 
fifth digits respectively; mc, metacarpus; mt, metatarsus; p, pha- 
langes; u, ulna; r, radius; t, tibia; /, fibula. — {After Marsh.) 



mal row, and the trapezium, trapezoid, magnum, and 



74 



ELEMENTS OF MAMMALIAN ANATOMY. 



unciform form the distal row. The scapholunar, easily 
distinguished because of its large size, articulates with the 
radius, cuneiform, unciform, magnum, trapezoid, and tra- 
pezium. The cuneiform articulates with the ulna, unci- 
form, pisiform, and scapho- 
lunar. The pisiform is next 
to the scapholunar in size. 
It projects prominently 
laterad from the cuneiform 
and articulates with the 
radius, ulna, and cuneiform. 
The trapezium is the small- 
est bone of the carpus . It is 





Mi 



A. B. 

Fig. 36. 

A, Dorsal aspect of left manus of cat : a, First phalanx of the pollex ; b, 

second or terminal phalanx; en, cuneiform; h, head of fourth meta- 
carpal; m, magnum; mt, metacarpal 4; n, claw; pi, pisiform; s, 
sesamoid bone ; st, scapholunar ; td, trapezoid ; tm, trapezium ; u, unci- 
form ; 1, 2, and 3, first, second, and third phalanges of the middle digit. 

B, Generalized type of carpus as found in lower vertebrates : c, Centrale; 

V intermedium or lunare; r, radiale or scaphoid; ra, radius; m, meta- 
carpals; u, ulnare or cuneiform; ul, ulna; 1, carpalia 1, or trapezium ; 
2, carpalia 2, or trapezoid; 3, carpalia 3, or magnum; 4 and 5, car- 
palia 4 and 5, or unciform. 



crescentic in shape and articulates with the scapholunar, 
trapezoid, and first and second metacarpals. The trap- 
ezoid is almost as small as the trapezium. It is distin- 
guished by its flatness. It articulates with the scapho- 



THE SKELETON. 



75 



lunar, magnum, second metacarpal, and trapezium. This 
bone is not visible on the palmar surface of the wrist. 
The magnum articulates with the 
scapholunar, trapezoid, unciform, 
and second, third, and fourth meta- / sc 

carpals. The unciform can be recog- 
nized by its wedge shape. It articu- 
lates with the scapholunar, cunei- 
form, magnum, and fourth and fifth 
metacarpals . Each carpal bone de- 
velops from a single center except 
the scapholunar, which develops 
from two centers. 

The typical arrangement of the 
vertebrate carpus is shown in figure 
36, B. The pisiform does not be- 
long to the cartilaginous skeleton, 
but is a sesamoid bone . In all mam- 
mals possessing five digits the an- 
lage of three bones in the proximal 
row, five bones in the distal row, 
and a central element occurs in the 
embryo, but through fusion of ele- 
ments a less number is present in 
most adults. Thus, in the cat the 
radiale and intermedium and cen- 
trale unite to form the scapholunar. 
In all forms carpalia 4 and 5 coal- 
esce to form the unciform. 

Metacarpus. — There are f^ve 
metacarpal bones forming the mid- 
dle region of the forefoot. They 
are named, beginning on the pollex side, first, second, 
third, fourth, and fifth metacarpals respectively. Each 



m 3 



Fig. 37. — Lateral As- 
pect of Left Fore- 
eimb of Equus. 

h, Humerus; m 3 , third 
metacarpal; ra 4 , fourth 
metacarpal; p, phalan- 
ges; r, radius; s, sesa- 
moid; sc, scapula; u, 
ulna; a, scaphoid; c, 
semilunar ; m, cunei- 
form; n, pisiform; w, 
magnum; u, unciform. 



7 6 ELEMENTS OF MAMMALIAN ANATOMY. 

bone consists of a proximal extremity or base, a middle 
portion or shaft, and a distal extremity or head (Fig. 36). 
These bones are curved so as to be slightly convex on the 
dorsal aspect. 

The number of metacarpals in mammals varies from 
one in Equus to five which are present in most orders. 
Nearly all the species of every order, except the Edentata 
and Ungulata, possess five metacarpals. In the pig and 
hippopotamus there are four metacarpals, in the rhi- 
noceros three, and in the camel, deer, sheep, and cow 
two. In the last three forms the metacarpals present are 
the third and fourth, which in the adult are coalesced 
into a single bone known as the cannon-bone. Remnants 
of the second and fifth metacarpals are present in the 
deer, sheep, and cow, as the small caudo-lateral hoofs 
indicate. The functional metacarpal present in the horse 
is the third. The reduction of metacarpals in the ances- 
tral forms of the horse is shown in figure 35, and will be 
referred to again in the description of the phalanges. 

Phalanges. — The cat has five toes or digits on the fore- 
foot, called pollex, index, medius, annulus, and minimus. 
Each digit, except the pollex, consists of three phalanges 
(Fig. 36). The pollex or thumb has only two phalanges. 
The row of phalanges articulating with the metacarpals 
is called the proximal, the terminal row the distal, and 
the remaining row the middle phalanges. Two small sesa- 
moid bones are attached on the volar side of the junction 
of each proximal phalanx with the metacarpal. Each 
distal phalanx has its proximal end produced caudal on 
the palmar aspect so that its articular surface faces 
dorsal. The distal phalanges terminate in claws which 
are retractile. 

The number of digits in the forefoot of Mammalia varies 
from one to five. Nearly all the species of every order 



THE SKELETON. 77 

except the Endentata and Ungulata possess five digits. 
The tapir has four functional digits. The cow, deer, 
sheep, and pig also have four digits, but only two are 
functional, the second and the fifth being atrophied and 
terminating in the small caudo-lateral hoofs which do not 
touch the ground. The rhinoceros has three functional 
digits, and the Equidae possess only one digit (Fig. 37), 
the third, though the atrophied remnants of the second 
and fourth metacarpals are present as splint bones which 
do not support phalanges. 

As before stated, the Ungulates are undoubtedly de- 
scendants of a five-toed ancestor of Eocene times. The 
evolution of the horse's limb and the reduction in the 
number of digits are shown in figure 35. Fossil remains 
of the ancestors of the horse have been found in western 
United States, Europe, and South America. Orohippus 
lived in the region of Wyoming, Montana, and Idaho 
probably more than 5,000,000 years ago, when that 
country was more or less marshy, and it was necessary 
that the mammals should possess a spreading foot which 
would not permit them to sink too deep into the mud. 
As the ground became firmer and preying Carnivora 
more numerous, the foot of the horse adapted itself to 
rapid flight over solid ground. Thus, through use and 
natural selection the third digit was enlarged at the 
expense of the other digits. Confirmation of this ances- 
tral history of the horse is found by an examination of 
the early embryonic stages. According to Ewart, a 
horse embryo 35 cm. long possesses quite well-developed 
second and fourth metacarpals terminating with pha- 
langeal structures. The ulna and radius of an embryo 
50 mm. long are strikingly similar to these same bones 
in Mesohippus. In a still younger embryo the ulna is 
complete and correspondingly as large as in Orohippus. 



78 ELEMENTS OF MAMMALIAN ANATOMY. 

As to the method of walking, mammals are spoken of 
as plantigrade, digitigrade, and unguligrade. The first 
mode of progression is exemplified by the bear, which 
places its metacarpals and phalanges flat on the ground 
in walking. The cat is digitigrade, walking on its toes. 
The horse and cow are unguligrade, as they walk upon 
the hoof. In some cases, as in the Cetacea, the forefoot 
is adapted for swimming instead of walking, and the 
number of phalanges to each digit is more than three. 

PRACTICAL QUESTIONS AND SUGGESTIONS. 

1. What bones compose the shoulder girdle? 

2. How is the thoracic limb attached to the trunk? 

3. What does the condition of the clavicle in the cat indicate as to 
its past history? 

4. Draw the mesal aspect of the scapula and label all parts. 

5. What is the significance of the coracoid process? 

6. Which processes of the scapula derive their names from their 
location and which from their shape? 

7. How do you distinguish the right from the left scapula? 

8. Draw the caudal aspect of the humerus and label all features. 

9. Describe what is seen in looking directly at the distal articulating 
surfaces of the humerus. 

10. How do you distinguish the right from the left humerus? 

1 1 . What features of the humerus derive their names from their shape ? 

12. Draw the mesal or inner aspect of the ulna and label all features. 

13. What features of the ulna derive their names from their form? 

14. How do you distinguish the right from the left ulna? 

15. Describe the articulations of the radius. 

16. Draw lateral aspect of radius and label all features. 

17. Describe the condition of the bones of forearm in the horse and 
its ancestors. 

18. In a five-month fetus of the horse the ulna is distinct from radius 
and complete, while in the mature animal but little more than the distal 
third remains, and is anchylosed to the radius. Explain significance 
of this fact. 

19. Draw ventral aspect of carpus and label all parts. 

20. Wherein is the chief difference between carpus of cat and man. 

21. Draw the lateral aspect of the third metacarpal and label all fea- 
tures. 



THE SKELETON. 79 

22. How do you distinguish the distal from the proximal end of the 
metacarpals ? 

23. Describe the variation in the number of metacarpals in mammals. 

24. Describe the usual arrangement of the phalanges in mammals 
having five digits. 

25. How do you distinguish a phalanx from a metacarpal? 

26. Give the number of functional digits in forelimb of dog, pig, cow, 
sheep, horse, and rabbit. 

27. Name some mammals with atrophied digits. 

28. What is the significance of these? 

29. In the evolution of the perissodactyls (odd-toed ungulates) de- 
scribe the order in which the digits are lost. 

30. In the Bovidae and Cervidae which two digits are functional? 



THE PELVIC LIMB. 

The pelvic or hind-limb of the cat is composed of the 
innominate bone, femur, patella, tibia, fibula, seven 
tarsals, five metatarsals, and twelve phalanges. 

The innominate bone is composed of four parts, the 
ilium, ischium, pubis (Figs. 21 and 38), and the small 
cotyloid bone. The ilium is the dorsal portion, extending 
down to and occupying about one-third of the acetabu- 
lum. The ischium includes the caudal portion of the 
bone, extending ventral and forming two-thirds of the 
boundary of the obturator foramen. The pubis is the 
ventral portion, possessing two rami, one projecting 
later ad to unite with the ilium, cotyloid, and ischium, 
and the other projecting caudad along the mid- ventral 
line, joining its fellow and the ischium. In young kittens 
the junction of these parts is plainly visible, but in adult 
specimens it is wholly obliterated. In old specimens the 
ischium and pubis become more or less anchylosed with 
their fellows in the mid- ventral line. The cephalic and 
dorsal border of the ilium is the crest (Fig. 39). The 
rough crescentic area on the mesal aspect is the auricular 
surface for articulation with the sacrum. The cephalic 



So 



ELEMENTS OF MAMMALIAN ANATOMY. 



rounded angle of the crest is the anterior superior spine. 
The anterior inferior spine is the small prominence 
cephalad from the ventral termination of the auricular 
surface. The posterior superior spine is the mesal pro- 
jection on the mid-dorsal border of the ilium, forming 
part of the auricular surface. 




Fig. 38. — Lateral Aspect of Left 
Innominate Bone. 

ct, Cotyloid bone; ac, acetabulum; 
il, ileo-pectineal eminence; as, 
anterior inferior spine; ass, an- 
terior superior spine. — (Modified 
after Jayne.) 




Fig. 39. — Ventral Aspect of the 
Innominate Bones. 

ac, Acetabulum ; ai, posterior infer- 
ior spine ; ar, auricular surface ; cr, 
crest ; et, cotyloid notch ; ip, ileo- 
pectineal eminence; is, body of 
ischium ; ob, obturator foramen ; 
pb, body of pubis; s, spine; sm, 
symphysis pubis; sp, spine of 
pubis; sr, surface of ilium for 
attachment of spinal muscles ; 
tb, tuberosity of the ischium. 



The ischium presents a spine on its dorsal border near 
the acetabulum. Between this spine and the posterior 
inferior spine of the ilium, is a shallow concavity termed 
the greater sciatic notch in distinction to the lesser sciatic 
notch between the spine of the ischium and the tuber- 



THE SKELETON. 




. n.a 5.4* 



osity. The acetabulum or cotyloid cavity forms the cup 
for the articulation of the femur. The interruption in its 
ventral border is the cotyloid 
notch, at whose base there is 
a depression for the attach- 
ment of the ligamentum teres 
holding the femur in place. 
The junction of the pubis with 
its fellow is known as the sym- 
physis. The cephalic portion 
of the bone lying on either side 
of this is called the body, the 
caudal part taking the name 
of ramus. The latter forms 
part of the boundary of the 
obturator foramen and meets 
the ramus of the ischium. This 
foramen gives passage to the 
obturator nerve and vessels. 

In the Sirenia, which have 
no pelvic limbs, the innomi- 
nate bones are rudimentary. 
In the Cetacea these bones are 
also rudimentary, which fact 
indicates that the ancestors of 
these forms possessed func- 
tional hind -limbs. 

The femur, or thigh-bone, 
may be recognized by its 
spherical head with a pit for 
the attachment of the liga- 
mentum teres which aids in holding the head in the ace- 
tabulum. 

The greater trochanter projects from the proximal end of 

7 




Fig. 



Lend. I 

40. — -Caudal Aspect of 
Femur. 
ex tub, External tuberosity; int< 
tub, internal tuberosity; ex 
end, external condyle ; int end, 
internal condyle; i end t, in- 
tercondylar notch or fossa; 
intch r, intertrochanteric 
ridge ; g trch, greater trochan- 
ter ; hd, head ; tin as, linea as- 
pera ; I trch, lesser trochanter ; 
nk, neck ; pit, pit for ^the liga- 
mentum teres ; tr fos, trochan- 
teric fossa or digital fossa. 



82 



ELEMENTS OF MAMMALIAN ANATOMY. 



the bone to a level 




Fig. 41. — Anterior 
or Cephalic As- 
pect of Right 
Tibia. 

at, Articulatory sur- 
face for the astrag- 
alus ; cr, crest ; et, ex- 
ternal tuberosity ; fc, 
facet for articulation 
with the fibula; im, 
internal malleolus ; 
it, internal tuberos- 
ity; lg, ligament of 
the patella cut off; 
tb, tubercle. 



nia have any trace 



with the head. On this process are 
inserted the pyriformis, gluteus me- 
dius, and gluteus minimus muscles, all 
of which originate on the innominate 
bone. The lesser trochanter is the small 
projection on the caudal aspect of the 
proximal portion of the bone (Fig. 40). 
The intertrochanteric ridge or posterior 
intertrochanteric line extends be- 
tween the two trochanters, and lying 
between this line and the neck is the 
digital fossa. The external and in- 
ternal condyles are the articulatory 
processes on the distal end of the bone. 
The blunt projections at their roots 
are the external and internal tuberos- 
ities. The inter condyloid notch forms 
the depression on the caudal aspect 
between the condyles. On the ceph- 
alic aspect is the trochlear surface for 
articulation with the patella. Two 
small sesamoid bones, the fabellae, are 
present on the caudal aspect of the 
condyles, but they are usually re- 
moved in preparing the skeleton. The 
linea as per a is the slightly roughened 
line beginning on the caudal side, dis- 
tal to the middle and extending proxi- 
mally a short distance, where it bifur- 
cates. 

The form of the femur varies but 
little among mammals having func- 
tional posterior limbs. No living Sire- 
of a femur, but a vestigial femur is 



THE SKELETON. 



83 



I 



present in Halitherium, a fossil form. The hind-limbs are 

wanting among the Cetacea, but in a few forms nodules 

of bone or cartilage may represent the 

femur. In most Perissodactyla and Ro- 

dentia, and in some Insectivora and a 

few fossil Carnivora, a third trochanter 

is present. 

The patella, or knee-cap (Fig. 21), is 
a sesamoid bone developed in the tendon 
of the quadriceps extensor muscle (Fig. 
52). It is somewhat the shape of an al- 
mond and about half its size. It articu- 
lates with the trochlea of the femur. 

The tibia is the larger bone of the crus. 
It presents two enlarged extremities and 
a shaft whose cross-section is triangular. 
It articulates with the femur and fibula 
proximally and the fibula and astragalus 
distally (Fig. 21). This is the longest 
bone in the cat's skeleton. Between the 
concave condyles on the proximal end is 
a notch giving attachment to the crucial 
ligament of the knee-joint (Figs. 41, 46). 

The prominences of the lateral and 
mesal aspects of the proximal extremity 
are the external and internal tuberosities 
respectively. Beneath the former is the 
facet for articulation with the fibula (Fig. 
41). The tubercle, a prominence on the 
cephalic side of this extremity, is for 
the insertion of the ligamentum patellce, 
which is really the termination of the 
tendon of the quadriceps extensor muscle (Fig. 52). On 
the caudal aspect between the condyles is the popliteal 



b 



f 



ar 

r 



Fig. 42. — Inner or 
Mesal Aspect 
of Right Fib- 
ula. 

a, Facet for tibia; 
ar, facet for as- 
tragalus; ex, ex- 
ternal malleolus; 
h, head ; s, shaft ; 
t, articular sur- 
face for tibia ; gr, 
groove for pero- 
neus longus mus- 
cle. 



84 ELEMENTS OF MAMMALIAN ANATOMY. 

notch. The sharp cephalic border of the bone forms the 
crest. On the distal extremity is a process, the internal 
malleolus, bearing two grooves, the more caudal of which 
shelters the tendon of the flexor longus digitorum muscle 
while the other is for the tibialis posticus (Fig. 52). A 
facet is present on the lateral aspect of this extremity for 
articulation with the fibula. 

The fibula in proportion to its length is the slenderest 
bone in the skeleton. It is the outer or lateral bone 
of the crus, and articulates proximally with the tibia 
and distally with the tibia and astragalus (Fig. 21). 
The proximal extremity is the head, upon which is a 
circular facet for articulation with the tibia. The sharp 
edge along the cephalic aspect of the shaft furnishes 
attachment to the interosseous membrane uniting the 
two bones of the crus. The mesal aspect of the distal 
extremity shows a prominent facet for articulation w T ith 
the astragalus. Immediately proximal to this is the 
articular surface for the tibia. From the lateral aspect 
projects the external malleolus, on the caudal side of 
which is a groove for the peroneus brevis muscle, and 
on the cephalic side is a slight depression for the pero- 
neous longus (Fig. 52). 

In many of the Mammalia the two bones of the crus 
are more or less united. In most of the Chiroptera and 
Ungulata the fibula is rudimentary. The middle portion 
of the fibula is absent in the horse and its distal portion 
is fused with the tibia (Fig. 35). The ancestor of the 
Equidae in Eocene times had a well-developed fibula, but 
in the evolution of the horse this bone has gradually 
diminished in size, as shown in the figure. 

The tarsus is composed of seven bones in two rows. 
The proximal row contains the os calcis, astragalus, and 
navicular or scaphoid; the distal row the cuboid, ecto- 



THE SKELETON. 



85 



cuneiform, mesocuneiform, and entocuneiform. The os 
calcis, or calcaneum, is the largest 
bone of the tarsus, being twice as 
long as broad (Fig. 43). Its caudal 
end presents a groove for the ten- 
don of the plantaris muscle. The 
peroneal tubercle is on the outer 
side of the distal extremity. The 
sustentaculum, a shelf-like pro- 
cess projecting from near the 
middle of the inner side, supports 
a facet for the tendon of the 
flexor longus digitorum muscle 

(Fig- 53). 

The astragalus lies on the inner 
or mesal side of the calcaneum and 
articulates with the tibia, fibula, cal- 
caneum, and navicular. The bone 
is composed of a body, neck, and 
head. The body is proximal and 
bears a trochlear surface for articu- 
lation with the tibia. The head 
bears a convex surface for articu- 
lation with the navicular. The neck 
is the constricted portion between 
the body and the head. 

The navicular lies on the mesal 
side of the foot and articulates with 
the remaining six bones of the tar- 
sus. It may be recognized by its 
deep concave surface for articula- 
tion with the astragalus, and also 

by the tuberosity, a process on its mesal plantar angle 
(Fig- 43)- 




Fig. 43. — Dorsal Aspect 
of Left Hind-foot. 

ag, Astragalus ; ar, articu- 
lar surface of the tibia ; 
cb, cuboid; ec, ectocu- 
neiform; gr, groove for 
the tendon of the plan- 
taris; h, head of the 
fourth metatarsal ; ic, 
entocuneiform; mc, 
mesocuneiform ; m, , hal- 
lux or first metatarsal ; 
ra 2 , ra 3 , ra 4 , and ra 5 , sec- 
ond, third, fourth, and 
fifth metatarsals ; nv, 
navicular or scaphoid; 
oc, os calcis, or calca- 
neum; 3, proximal row 
of phalanges; 2, middle 
row of phalanges ; 1 , dis- 
tal row of phalanges. 



86 ELEMENTS OF MAMMALIAN ANATOMY. 

The entocuneiform is next to the smallest bone of the 
tarsus. It articulates with the navicular, mesocuneiform, 
and first and second metatarsals. The mesocuneiform is 
a wedge-shaped bone and the smallest element of the 
tarsus. It articulates with the other two cuneiforms, 
the navicular and second metatarsal. The ectocuneijorm 
may be_j~ecognized by a strong hook-like process on its 
plantar surface. It articulates with the navicular, meso- 
cuneiform, cuboid, and second and third metatarsals. 

The cuboid is the lateral bone of the distal row. It 
may be recognized by the deep groove on its plantar 
surface which shelters the tendon of the peroneus longus 
muscle. 

The typical arrangement of the tarsal elements in ver- 
tebrates is similar to that of the carpus. Three bones, 
a tibiale, intermedium, and fibular e, compose the proximal 
row, while five tars alia form the distal row. The centrale 
occupies the center of the tarsal region. In the adult 
mammal fusion of some of these elements occurs, so that 
not more than seven distinct bones are present in any 
form. The astragalus contains the tibiale and inter- 
medium, while the fourth and fifth tarsalia form the 
cuboid. 

The metatarsus consists of five bones, the first of which 
is rudimentary, while the other four are longer than the 
metacarpus, which they resemble (Fig. 43). The first 
metatarsal is smaller than any bone of the tarsus. It 
articulates with the entocuneiform and is also in contact 
with the second metatarsal. The four long metatarsals 
have a slight dorsal convexity, each one consisting of a 
base or enlarged proximal part, a shaft or middle portion, 
and a head or distal rounded articular process. On the 
plantar surface of the head of each metatarsal is a median 
spine, on each side of which is a concavity for a sesamoid 



THE SKELETON. 87 

bone. These sesamoid bones are frequently lost in clean- 
ing the skeleton. 

The number of functional metatarsals in mammals 
varies from one to five. Usually the number of meta- 
carpals and metatarsals is the same, but in the tapir 
there are four metacarpals and but three metatarsals. 
All Monotremata, Carnivora, and Primates have five 
metatarsals, but in the cats, dogs, and hyenas the first 
metacarpal is vestigial. In early geological times all 
mammals possessed five metatarsals, the number of 
which in many cases has gradually diminished owing to 
environment, as is shown in the phylogeny of the horse 
(Fig. 35). 

The Kquidae possess but one functional metatarsal 
and two rudimentary ones, although Orohippus, the an- 
cestor of the horse, had three functional metatarsals. 

The phalanges of the cat's foot are twelve in number. 
Each metatarsal except the first supports three phalanges. 
The proximal phalanges are the stoutest, and the distal 
the smallest. Each distal phalanx bears a claw. 

In all five-toed mammals, such as Primates, there are 
fourteen phalanges, each digit being composed of three, 
except the hallux, which has two. 

PRACTICAL QUESTIONS AND SUGGESTIONS. 

1. Describe the articulations of the innominate bone. 

2. How do you distinguish the cephalic from the caudal aspect of 
the os innominatum? 

3. Which processes derive their names from their location? 

4. Draw the lateral aspect of the os innominatum and label all fea- 
tures. 

5. Name the four parts of the bone in order of size. 

6. What two orders of mammals have no pelvic limbs? 

7. Describe what is seen in viewing the femur from the cephalic 
aspect. 

8. Name the processes of the femur. 

9. Draw the distal aspect of the femur. 



88 ELEMENTS OF MAMMALIAN ANATOMY. 

10. How do you distinguish the right from the left femur? 

11. Describe the patella. 

12. Draw the caudal aspect of the tibia and label all features. 

13. How do you distinguish the right from the left tibia? 

14. Describe the articulations of the fibula. 

15. What features distinguish the proximal from the distal extremities 
of the fibula? 

16. Write 100 words describing the crus in other mammals than the 
cat. 

17. Draw the ventral aspect of the tarsus and label all parts. 

18. Which of the tarsals support metatarsals? 

19. Name the tarsals in order of size. 

20. Draw the lateral aspect of the third metatarsal. 

21. How do you distinguish a metatarsal from a metacarpal? 

22. How do you distinguish the proximal from the distal end of a 
metatarsal? 

23. Describe the condition of the metatarsals in various mammals. 

24. In most mammals how many phalanges to each digit? 

25. What artiodactyls have you seen with only two functional digits 
on the posterior limbs? 



THE JOINTS. 



The study of the articulation of the bones and the 
ligaments holding them in place is known as syndesmol- 
ogy. There are three general classes of articulations: 
Synarthroses, or immovable joints; amphiarthroses, or 
joints with slight motion; and diarthroses, or joints freely 
movable. A synarthrodal joint is exemplified in the 
sutures between the bones of the skull. The two surfaces 
of bone are separated by fibrous membrane only. An 
amphiarthrodal articulation occurs between the bodies 
of the vertebrae and also in the union of the sacrum 
with the ilium. In the articula- 
tion of the vertebrae the con- 
tiguous surfaces of the bone are 
faced by flattened discs of fibro- 
cartilage (Fig. 21). 

The diarthrodal articulation is 
exemplified in all joints allowing 
free motion. Such joints are 
composed of the following parts : 
the ends of two bones having 
their contiguous surfaces covered 
with cartilage; a synovial mem- 
brane forming a short tube whose 
ends are closed by the cartilagin- 
ous articulating surfaces; and 

several ligaments varying in number from two or three to 
a dozen (Fig. 44) . There are four kinds of the diarthrosis : 
the arthrodia, or gliding joint, which occurs between the 




Fig. 44. — Diagram of a 
Diarthrodal Joint. 

ar, Articulatory cartilage ; Ig, 
ligament ; sn, synovial 
membrane ; sy, synovial 
fluid in synovial cavity; t, 
tibia ; v, femur. 



9° 



ELEMENTS OF MAMMALIAN ANATOMY. 



bones of the carpus; the enarthrosis, or ball-and-socket 
joint, such as at the hip or shoulder; the ginglymus, or 
hinge joint, exemplified at the elbow and knee; and the 
rotatoria, or pivot joint, formed by the articulation of 

the axis and atlas. 

As the knee-joint can be 
readily dissected and the 
parts well displayed, it is 
here described somewhat in 
detail. The leg should be 
detached at the hip-joint 
and the muscles largely re- 
moved, taking care in the 
immediate neighborhood of 
the knee that the ligaments 
are not cut. There are eight 
ligaments to this j oint . The 
anterior ligament, or liga- 
ment of the patella (Fig. 45), 
extending from the patella 
to the anterior tubercle on 
the tibia, is the strongest 
ligament of the knee-joint, 
and is really a continuation 
of the tendon of the quadri- 
ceps extensor muscle. The 
capsular ligament, which 
entirely surrounds the joint 




Fig. 45. — Lateral Aspect of Dis- 
sected Knee-joint. 

ad, Adipose tissue; ax, antero-in- 
ternal ligament of the meniscus ; 
cp, capsular ligament cut and re- 
flected mesad; hi, tendon of the 
popliteus muscle pulled proximad 
to display sc; en, caudal projec- 
tion of condyle of tibia; ex, an- 
tero-external ligament of the 
meniscus ; ex, external lateral liga- 
ment; fb, fibula; fm, femur; Ig, 
ligament of the quadriceps exten- 
sor muscle ; pt, patella ; sc, exter- 
nal or lateral meniscus ; sent, mesal 
or internal meniscus ; tf, tibiofibu- 
lar ligament ; tb, tibia. 



except in the places occu- 
pied by the anterior and lateral ligaments, consists of 
two parts, a cephalic and a caudal. The former is seen 
on either side of the anterior ligament, extending from 
the femur to the tibia as a thick membrane, and more 
laterally being attached to the menisci. The caudal 



THE JOINTS. 



91 




part extends from the fabellse and the femur to the tibia 
and menisci. 

The external lateral ligament proceeds from the exter- 
nal tuberosity of the femur to the 
head of the fibula. The internal 
lateral ligament, much shorter than 
the external one, extends from the 
internal tuberosity of the femur to 
the internal tuberosity of the tibia. 
The anterior and capsular ligaments 
must be cut in order to see the cru- 
cial ligaments, which are short, and 
cross each other in the region of the 
intercondylar notch. The posterior 
crucial extends from the caudal 
margin of the head of the tibia to 
the mesal cephalic angle of the in- 
tercondyloid notch of the femur. 
The anterior crucial extends from 
the summit of the tibia to the cau- 
dolateral angle of the intercondy- 
loid notch. The tibiofibular liga- 
ment is very short, extending from 
the head of the fibula to the outer 
tuberosity of the tibia. In addition 
to these ligaments, there are four 
bands uniting the menisci to the 
bones. The menisci or semilunar 
cartilages are two biconcave cartila- 
ginous plates, about one millimeter 
thick, interposed between the con- 
dyles of the femur and tibia. 

The synovial membrane is a very thin transparent 
sheet lying within the capsular sheath of the joint. It 



Fig. 46. — Caudal Aspect 
of Knee-joint with 
Capsular Ligament 
Cut. 

ac, Anterior crucial liga- 
ment ; ar, articular sur- 
face of condyle of tibia ; 
en, condyle of femur ; cp, 
capsular ligament cut 
along the line Ig and re- 
flected proximad ; ex, 
external lateral liga- 
ment; fb, fibula; fm, 
femur; in, internal lat- 
eral ligament; Ig, cut 
edge of capsular liga- 
ment ;" pc, posterior cru- 
cial ligament; pi, pos- 
terior external ligament 
of the meniscus; sm, 
mesal or internal men- 
iscus ; sme, lateral or ex- 
ternal meniscus ; tf, tib- 
iofibular ligament ; tb, 
tibia. 



Q2 ELEMENTS OF MAMMALIAN ANATOMY. 

secretes the white glairy synovia for lubricating the joint. 
The synovial fluid and membrane may be demonstrated 
by cutting open a fresh joint obtained from the butcher- 
shop (Fig. 4). 

All other freely movable joints are similar in structure 
to the knee-joint, but have no menisci and fewer liga- 
ments. The shoulder-joint has only two or three liga- 
ments, the most important of which is the capsular. The 
elbow-joint has four ligaments and the hip-joint only two. 
In the ankle-joint there are eight ligaments in addition 
to the capsular. 

These ligaments which bind the joints consist of white 
fibrous connective tissue which under the microscope is 
seen to be composed of parallel and interlacing fibers. 
They are very tough and have but little elasticity, so 
that the joints are seldom dislocated (Fig. 11). 



PRACTICAL QUESTIONS AND SUGGESTIONS. 

1. Give three examples of each of the three general classes of joints. 

2. Explain difference in anatomy of the three classes of joints. 

3. Without aid of the microscope can you detect any differences 
between a ligament and a tendon? 

4. By removing the capsular ligament describe the ligaments that 
can be displayed on the lateral and caudal aspects of the knee-joint. 

5. After bringing to view by dissection as many ligaments as possible 
on inner aspect of knee-joint, draw and label all parts. 

6. Draw the menisci. 

7. By careful dissection note the ligaments present in the hip-joint. 

8. How many ligaments can you find in the shoulder-joint? 

9. In what joints is synovia present? 

10. Cut a very thin slice of articular cartilage about a millimeter square, 
mount in dilute acetic acid, and make drawing as seen under the micro- 
scope. 



THE MUSCLES. 

The study of the muscular system is known as myology. 
The muscles are of two kinds : voluntary, which are under 
the control of the will; and involuntary, which cannot be 
controlled by the will. All muscles moving the bones are 
voluntary and are supplied with branches of the cerebro- 
spinal nerves. Examples of involuntary muscles are 
found in the walls of the alimentary canal, the ureter, 
bronchial tubes, and blood-vessels. These are supplied 
with nerves from the sympathetic nervous system (Fig. 
91). The structure of a voluntary muscle may be seen 
by teasing a small piece on a slide in a drop of water, 
covering with a cover-glass, and examining with the 
compound microscope. It is composed of striated fibers 
from one to fifteen centimeters in length, while involun- 
tary muscle is composed of cells more or less spindle- 
shaped and non-striated, except in the heart (Figs. 8 
and 10). 

There are over five hundred voluntary muscles in the 
cat, each of which is usually attached at either end to 
the periosteum of a bone. That point of attachment 
which is the center of motion is known as the origin of 
the muscle, and is usually more proximad than the 
insertion of the muscle. In the case of the biceps, its 
origin is on the scapula and its insertion on the radius. 
Usually a muscle originates and terminates in a white 
glistening cord called a tendon, composed for the most part 
of white fibrous tissue (Fig. 11). 

Each muscle-fiber is surrounded by a transparent 

93 



94 ELEMENTS OF MAMMALIAN ANATOMY. 

elastic sheath, the sar oolemma. A number of fibers 
bound together by a loose connective tissue, and the 
whole enveloped by an extension of the same, is a fascic- 
ulus. The tissue connecting the fibers is the endomy- 
sium, while that enveloping the fasciculus is the peri- 
mysium. A number of fasciculi bound together in a 
sheath, the epimysium, constitutes the entire muscle. 
The epimysium is merely a deflected portion of the 
sheath enveloping the fasciculus. It is visible to the 
naked eye as a thin shining sheath beneath the fascia 
which covers the muscles and binds them together. 

According to function, muscles are spoken of as flexors, 
extensors, adductors, abductors, rotators, elevators, depres- 
sors, and sphincters. A flexor muscle is one which by its 
contraction bends a limb or any portion of it. An 
extensor muscle is the antagonist of a flexor and serves 
to bring the two long bones into line. An abductor 
muscle is the one inserted on a long bone, which it draws 
laterad from the axis of the limb or the sagittal plane 
of the body. An adductor muscle is the antagonist of 
an abductor. The pectoral muscles are adductors of the 
forelimb. A rotator muscle is one which produces more 
or less of a rotatory motion in the bone upon which it 
is inserted. A rotator muscle is exemplified in the obtu- 
rators, which arise on the innominate bone and are 
inserted in the digital fossa of the femur. An elevator 
muscle is represented by the temporal, extending from 
the temporal bone to the mandible, which it elevates. 
A depressor muscle is the antagonist of an elevator. 
The digastric is a depressor of the mandible. A sphincter 
muscle is one surrounding an orifice which it closes by 
contraction. The orbicularis oris in the lips is an ex- 
ample. 

Muscles are named according to their function, shape, 



THE MUSCLES. 95 

or part to which they are attached. Thus the sterno- 
mastoid muscle arises on the sternum and is inserted on 
the mastoid process of the skull. The latissimus dorsi is 
so named because it is a very broad muscle (Fig. 47) 
and occupies the dorsal part of the cat's body. The 
extensor communis digitorum muscle signifies by its 
name that it is the common extensor of the digits. 



DISSECTION OF THE MUSCLES. 

Since the other systems are of more importance from 
the standpoint of comparative anatomy and physiology 
than the muscular, only the more important muscles will 
be described. Great care should be exercised in removing 
the skin of the cat, in order that such superficial muscles 
as the platysma myoides on the neck and side of the 
face, and occipitofrontalis, may not be cut away. The 
skin is attached to the underlying muscles by the super- 
ficial fascia, a fibrous areolar tissue, which contains the 
subcutaneous fat more or less abundant in all specimens. 
The deep fascia is the fibrous and membranous layer 
of dense tissue lying close against the muscles and dipping 
down between them. The stronger parts of this fascia 
are called aponeuroses. 

Directions for Dissection. — Dissection does not mean 
the cutting up, but the intelligent separation of one 
organ from another without removing the same. The 
muscles should not be cut loose from their origin or 
insertion, but merely separated from each other by cut- 
ting the deep fascia in the longitudinal direction of the 
muscle. If it is necessary to remove a muscle for dis- 
playing those beneath, it should be cut transversely in 
the middle and the two parts reflected. No portion of a 
muscle or other tissue should be removed without know- 



90 ELEMENTS OF MAMMALIAN ANATOMY. 

ing what it is and noticing carefully its relation to the 
surrounding parts. The specimen under dissection 
should be securely nailed to the tray so that the muscles 
are made tense. When the parts become dry, they 
should be thoroughly wet with water. If the formalin 
in which the specimen has been preserved is irritating 
to the mucous membrane of the dissector, a half liter 
of 5% ammonium hydrate should be poured over the 
specimen. 

The muscles of the following table are arranged accord- 
ing to location, but they need not be dissected in the 
order named. Some classes having time for the study 
of one-half or even one-third of the muscles here de- 
scribed will be able by the use of the table and the illus- 
trations to become familiar with the functions and the 
relations of any muscles the instructor may wish to 
assign for study. The student should note carefully the 
muscles which together effect a certain motion, such as 
the flexion of the forearm or the extension of the digits. 






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98 



Fig. 47. — Ventral Aspect of the Cephalic Half of the Cat. The 
superficial muscles have been removed from the left side and the 
scapula reflected laterad to display the serratus and adjacent muscles. 

a, Triceps; b, triceps; car, carotid artery; c, c„ and c. : , scalene muscles; 
cph, cephalohumeral ; ere, coracobrachialis ; dg, digastric; ds, cut end 
of the digastric; ext, external oblique; /, inferior constrictor; gh, 
geniohyoid; h, humerus; i, scalene; ic, triangularis sterni; int, in- 
ternal oblique ; j, hyoglossus ; k, styloglossus ; /, rectus lateralis ; Id, 
latissimus dorsi reflected lateral and much of the reflected portion 
cut off; h, levator anguli scapulae; m, longus colli; man, mandible; 
mas, masseter; mh, mylohyoid; md, median ventral line; n, fascicl 
aponeurosis of the external oblique; pc u pc 2 , pc 3 , and pc if first, second, 
third, and fourth parts of the pectoralis muscle; pet, portion of the 
pectoral muscle of the left side ; ret, left rectus abdominalis ; sh, sterno- 
hyoid ; s)^, sternohyoid of the left side. with its middle portion removed ; 
std, sternothyroid ; stm, sternomastoid ; si, portion of left sterno- 
mastoid; sub, subscapularis ; sps, suprascapularis ; tm, teres major; 
tr, triceps; x, cleidomastoid ; 1, 2, 3, 7, 8, and 9, ribs; 5, trachea. 




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Limb. 

a, Cephalic part of the ento-triceps; an, annular ligament; am, abductor 
minimi digiti; c, extensor carpi radialis brevior; del, acromiodeltoid ; 
dl, biceps; ecd, extensor communis digitorum; ecrl, extensor carpi 
radialis longior, whose tendon is marked m; emd, extensor minimi 
digiii; ei, extensor indicis; exul, extensor carpi ulnaris; eom, extensor 
ossis metacarpi pollicis; ex, ulnar head of the flexor carpi ulnaris; 
fu, flexor profundus digitorum; hu, humerus; *, caudal part of the 
ento-triceps ; o, olecranon process of the ulna ; p, claw of first digit : 
pect, portion of the pectoralis; r, region of the head of the radius; 
sp, spine of the scapula ; tr v ecto-triceps with its middle portion cut 
out. 






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112 



Fig 50-Mbsai, or Inner Aspect of the Muscles of the ForElimb. 

a Supracondyloid ridge of humerus ■ ah, abductor poliicis; b, humerus; 

' c JSSSd head of the flexor carpi ulnaris; cp, emo-tnceps J m- 

emon ofa tendonof flexor sublimis d^torum ^ « ^ulnar tarfrf 

K ^tfiS profundus digitorum ; fc the £ portion of the 
flexor sublimis arising from the palmans longUb,- ffc comm 
of the flexor profundus digitorum; /far, flexor profundus 
A flexor profundus digitorum; *, pronator quadratus; t flexor carpi 
radians- o short part of the ento-triceps ; ol, oecranon process ; of, 
teXous loops; peat, pectoralis cut off; /,*, origin of the palmans 
toS^whi^ w reflwtedl caudad; pt, pronator teres ;, r, -ento-tnceps ; 
ro ^racobrLhialis; #, split in the tendon of the flexor sublimis re- 
vealed IS cutting Way the tendinous loop; j*. supraspinal; si, 
lu^tor lSSg^?^, tires major; tb, the head of the humerus;^ 
a tendon of the flexor profundus digitorum whose portion between 
the two letters is cut out to display the insertion of & 



Fig. 51. — Ventral Aspect of Muscles of Caudal Portion of Trui 

and Thigh. 

a, Transversalis abdominis becoming aponeurotic; add, adductor mag- 
nus; c, pectineus, exob, external oblique, whose aponeurosis on the 
left side is removed; /, aponeurosis of external oblique; grc, gracilis 
with its middle part cut out on the left side; m, median ventral line; 
ps, psoas magnus ; p, penis ; rcj, rectus femoris ; rcf, rectus abdominis ; 
sar, sartorius with its middle part cut out on the left side; smb, semi- 
membranosus; smt, semitendinosus; spntc, spermatic cord; t, apo- 
neurosis; trs, internal oblique with a rectangular piece cut out to 
show the rectus and transversalis; tvg, tensor vaginae femoris;- £r, 
testicle; vi, vastus internus , x, external abdominal ring. 



Fig. 52. — Lateral Aspect of the Muscles of the Leg with the Glu- 
tei, Tensor Vagin.e Femoris, Semitendinosus, and Biceps Fem- 
oris Removed. 

a, Portion of semimembranosus; ab, adductor magnus; b, peroneus ter- 
tius; c, abductor ossis metatarsi; ct, cut surface of the vastus ex- 
ternus ; d, peroneus brevis ; eld, extensQr longus digitorum pedis ; 
gas, gastrocnemius; /, tendinous loop; lp, annular ligament; It, ex- 
ternal lateral ligament of the knee-joint; Ig, tendon of the extensor 
longus digitorum pedis; o, tendinous arch of the peroneus longus; 
oc, os calcis; pi, peroneus longus; ret, rectus femoris; /, ligament ura 
patellae: tr, greater trochanter ; ts, soleus; tg, tendon of gastrocnemius; 
tpl, tendon of the plantaris; tb, tibiali <■■%, vastus externus 

ch a piece cut out. 







ret 




ii4 



ELEMENTS OF MAMMALIAN ANATOMY. 




The muscles in the different orders of mammals have 
the same general arrangement. Over four hundred mus- 
cles occurring in the cat are found in 
man and have approximately the same 
relative location and function, and the 

/same nerve-supply. The size and the 
etilf z '/f shape of the muscles may vary some- 
what in accordance with the habits of 
the animal. The pectoralis in the cat 
consists of five parts, while in man there 
are only two parts. The biceps is a sim- 
ple muscle in the cat, but in man it has 
two well-defined heads. The muscles for 
moving the ear, which are well developed 
in the horse, cow, and cat, are exceed- 
ingly rudimentary in man. The Ceta- 
cea and Sirenia possess fewer muscles 
than the other orders of mammals, as 
they have no hind-limbs. These few re- 
marks serve to show that a familiarity 



j-ac 



ah 



» 



Fig. 53. — Caudal Aspect of the Muscles of the 
Crus and Foot with the Gastrocnemius, Sol- 
eus, and plantaris removed. 
ad, Adductor ; ac, tendon of Achilles ; ab, abductor 
ossis metatarsi; eg, external head of gastrocne- 
mius; fb, flexor brevis digitorum cut at x and 
turned aside ; fd, flexor longus digitorum ; fl, flexor 
longus hallucis; i, peroneus longus; /. peroneus 
brevis ; Ip, tendinous loop through which pass the 
tendons of the flexor brevis digitorum and the 
flexor longus digitorum ; n, cut tendons of fb; 
o, plantaris over the tuberosity of the os calcis ; 
p, tendon of the peroneus brevis ; pi, tendon of 
the plantaris, whose proximal portion is cut away ; 
r, tendon of the flexor longus digitorum pedis cut 
off as it passes through the slit in the flexor brevis 
digitorum ; s, tendon of the flexor brevis digitorum 
split for the transmission of the tendon of the 
flexor longus digitorum pedis ; s, soleus ; /, tendon of the flexor longus digit- 
orum pedis; x, plantaris giving origin to the flexor brevis digitorum. 



n 



THE MUSCLES. 115 

with the muscles of any one mammal guarantees a general^ 
knowledge of the muscular system of all mammals. 

PRACTICAL QUESTIONS AND SUGGESTIONS. 

1. Describe the two kinds of muscles. 

2. Draw a diagrammatic cross-section of the palmaris longus muscle 
representing the relation of the fibers, fasciculi, sarcolemma, endomy- 
sium, and epimysium. 

3. Describe an example of each class of muscles as to function. 

4. Which muscles of the head and neck region derive their names 
from their function? 

5. Describe the chief muscles moving the mandible. 

6. Describe the muscles lying ventral to the trachea. 

7. Name three important muscles attaching the thoracic limb to 
the trunk. 

8. Draw the caudal aspect of the triceps muscle. 
9 What muscles flex the forearm on the arm? 

10. Name the chief extensors and flexors of the digits. 

1 1 . On what process of the humerus do several of the flexors of the 
manus arise? 

12. On what process of the humerus do most of the extensors of the 
manus arise? 

13. Draw the outline of the ventral aspect of the flexor profundus 
digitorum as it would appear detached from limb and with origins slightly 
separated. 

14. Draw cephalic aspect of the radius and mark the areas to which 
the muscles are attached and the names of the same. 

15. What muscles flex the manus on the forearm? 

16. Describe the muscles extending the manus on the forearm. 

17. What muscles in the forearm region derive their names from their 
function and location? 

18. Describe the large adductor of the thoracic limb. 

19. Describe the muscles serving to move the humerus in four direc- 
tions. 

20. Describe the location and the use of the tendinous loops in the 
manus. 

21. What muscles form the ventral and lateral walls of the abdomen? 

22. Describe from your dissection four muscles causing the movement 
of the ribs. 

23. After removing the biceps femoris and sartorius, and dissecting 
the muscles on the lateral aspect of the thigh, draw the muscles visible 
on the lateral aspect, and label. 

24. Name the muscles flexing the crus on the thigh. 



Il6 ELEMENTS OF MAMMALIAN ANATOMY. 

25. Describe from your dissection the muscles extending the crus on 
the thigh. 

26. Describe the muscles forming the calf of the leg. 

27. What muscles are the opponents of the adductor magnus? 

28. Draw the plantar aspect of pes showing the superficial muscles, and 
label all the features. 

29. Describe three muscles moving the digits. 

30. Show by drawing the location of the muscles flexing the pes on 
the tibia and label all the features. 



ORGANS OF DIGESTION, 

A young lean cat which has had no food for twenty- 
four hours is the best subject for the demonstration of 
the digestive system. Directions for preparing the 
specimen are given in the chapter on technique. 

The digestive system (Figs. 54 and 55) consists of 
the alimentary canal and the accessory glands of diges- 
tion. The canal is made up of the mouth, pharynx, 
esophagus, stomach, small intestine, and large intestine. 
Its entire length is about five times that of the cat from 
the tip of the nose to the root of the tail. The accessory 
glands consist of five pairs of salivary glands, the liver, 
and the pancreas. 

THE MOUTH. 

The mouth is bounded cephalad by the lips, laterally 
by the cheeks, and dorsally by the palate, where the 
mucous membrane lies in seven or eight transverse 
ridges or rugae, and caudally depends from the palatine 
bones forming the velum palati. To display the anatomy 
of the mouth, one should remove the right half of the 
mandible. From either side of the velum palati two 
folds of membrane diverge as they extend to the floor 
of the mouth at the root of the tongue. The cephalic 
fold is the anterior pillar and the caudal one is the poste- 
rior pillar of the fauces (Fig. 55). The caudal portion 
of the mouth between these folds is known as the fauces. 
It opens into the pharynx. On either side of the tongue 
between the two pillars is a crescentic depression holding 

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ORGANS OF DIGESTION. 



119 



a tonsil. In man, the tonsils sometimes become in 
flamed and enlarged, giving 
rise to a disease called tonsil- 
litis. The tonsil is a compound 
lymphatic gland whose func- 
tion is unknown. 

Folds of mucous membrane 
called f rena bind the lips to the 
gums, which are composed of 
dense fibrous tissue investing 
the alveolar margins of the 
jaw-bones. The mucous lining 
of the mouth contains many 
simple mucous glands invisi- 
ble to the naked eye. Those 
of the lips are called labial, of 
the cheeks, buccal, and of the 
palate, palatine glands. 

The tongue lying in the floor 
of the mouth is a muscular 
mass composed of the genio- 
hyoglossus, lingualis superfici- 
alis superior and inferior, sty- 
loglossus, and hyoglossus mus- 
cles. Caudally it is attached 
to the hyoid bone. Its invest- 
ment of mucous membrane is 
formed into a fold beneath it, 
called the frenum linguae. The 
dorsal surface of the tongue 
displays four kinds of papillae 
(Fig. 55) : The circumvallate, 

numbering from six to eight arranged in a V shape near 
the root; the flat, very numerous at the root; the conical, 




Fig. 55. — Dorsal Aspect of 
the Tongue and Larynx. 

at, Arytenoid cartilage; af, an- 
terior pillar of the fauces ; cc, 
crico-epiglottic ligament; cd, 
true vocal cords; cv, circum- 
vallate papilla ; ep, epiglottis ; 
fl, flat papilla; fg, fungiform 
papilla ; fr, filiform papilla ; gl, 
glottis; hy, epihyal bone cut 
off; i, false vocal cord; ce, lu- 
men of the esophagus, which 
is cut off just as it opens into 
the pharynx ; pf, posterior pil- 
lar of the fauces ; tn, tonsil. 



120 ELEMENTS OF MAMMALIAN ANATOMY. 

most numerous and thickly set over the entire dorsal 
aspect; and the fungiform, which are blunt and located 
more thickly on the sides and near the tip of the tongue 
(Fig. 55)- 

The Teeth. — During the first year the cat develops 
twenty-six teeth, known as the deciduous or temporary 
set, as they are later replaced by a permanent set. The 
three parts of a tooth are the crown, neck, and fang (Fig. 
57). The crown may be divided into several portions 
called cusps. A tooth split longitudinally presents the 
following four features (Fig. 56) : the 
enamel, a hard glistening substance 
covering the entire crown of the tooth 
down to the neck; the cement, a bony 
substance investing the fang ; the den- 
tine, forming the interior hard portion 
of the tooth ; and the pulp cavity, con- 
Fig. 56. — Longitu- taining in the recent state the nerve- 

dinal Section of an( j blood-vessels. The enamel con- 
the Canine Tooth. 

c, Crown; cr, cement; sists mostly of the phosphate of lime. 

d, dentine ; e, en- jj- j s -foe covering: which when broken 

amel; /, fang; m, 

pulp-cavity ;n, neck, permits the tooth to decay. 

In an adult cat there are in each 
half of the upper jaw three incisors, one canine, three pre- 
molars, and one molar (Fig. 57). In each half of the lower 
jaw there are three incisors, one canine, two premolars, 
and one molar. The permanent dentition of the cat is 
therefore expressed by the formula i f , c \, pm f , m \. 

The upper incisor teeth are small and undivided both 
as to root and crown. They are scarcely one-third as 
long as the canine and are planted in the alveoli or 
sockets of the premaxillary. The remaining teeth of 
this jaw are in the maxilla. The canine or eye tooth 
is the longest and likewise is undivided as to root and 




ORGANS OF DIGESTION. 121 

crown. The next three teeth are known as the pre- 
molars. They vary much in size. The anterior one 
is the smallest, being about the size of the incisors. Its 
crown is usually simple, although occasionally there is 
seen a small posterior cusp, called triticone, in distinction 
to the main cusp or protocone. The root is usually 
composed of only one fang. The second premolar is 
much larger than the first. Its crown presents a large 
median cusp, or protocone; a very small cusp, triticone, 

■M 



CTyWil 











" " f * J 7 s 






■j 

Fig. 57. — Lateral Aspect of the Permanent Dentition of the Cat. 

*,, i. 2t i. A , First, second, and third incisors of the upper jaw; c, canine; p lt 
p. 2) and pz, first, second, and third premolars; m, molar; 1, 2, 3, the 
incisors of the lower jaw; 4, canine; 5 and 6, first and second pre- 
molars; 7, molar; c, cingulum ; d, deuterocone; m, metaconid; m, mo- 
lar; pt, protoconid; re, protocone; td, talonid; t, talon; tr, triticone. 

on the posterior side of the protocone half-way between 
its base and apex; and a basal cusp, the talon, on the 
posterior side of the base of the tooth. The prominent 
ridge encircling the tooth at its base is the cingulum. 
The root is composed of two fangs. 

The third premolar or carnassial tooth is fully twice 
as large as the second premolar. Its protocone is the 
large central cusp, posterior to which is the large triti- 
cone. At the mesal anterior angle is the deuterocone. 



122 ELEMENTS 01 MAMMALIAN ANATOMY. 

The small projection at the lateral anterior angle is the 
protostyle. The root of the tooth usually consists of 
three fangs. The posterior tooth in the maxilla is 
called the molar, since it is the only one not preceded 
by a milk tooth. It is very small and its crown presents 
a grinding surface instead of a cutting one. Its root 
consists of two fangs. 

Each half of the mandible holds three incisors, one 
canine, two premolars, and one molar. The incisors and 
canine are so similar to the upper ones that they need 
no further description. The first premolar presents a 
principal cusp or protoconid, a lower small cusp or 
metaconid. and a projection, on the posterior side of 
the base, known as the talonid. A cingulum or encircling 
ridge is also present at the base of the tooth. The root 
consists of two fangs. 

The second premolar is very similar to the first except 
that it is larger and presents an anterior basal cusp in 
addition to the others. The lower molar, sometimes 
called the sectorial, because it shears against the upper 
sectorial or carnassial premolar, presents two nearly 
equal cusps., the protoconid and the paraconid. The 
root consists of two fangs, the anterior of which is the 
larger. 

The deciduous or milk teeth begin to appear above the 
gums when the kitten is two weeks old. The incisors 
and the canine appear first, then the second and third 
molars. The first upper molars do not appear till the 
kitten is about six weeks old. According to Jayne, the 
deciduous dentition is complete at the end of the second 
month. At the end of the fourth month the milk incisors 
are being displaced by the permanent teeth. The 
formula for the temporary set is di f , dc }. dm f. 

Teeth are present in nearly all adult mammals. The 



ORGANS OF DIGESTION. 1 23 

whalebone whales, the duck-bill, and some of the ant- 
eaters have no teeth in the adult state, but teeth are 
present during their embryonic life. The Echidna shows 
no evidence of teeth at any time. Most mammals have 
two distinct sets of teeth, known as the milk or deciduous 
set, and the permanent set. In the Marsupialia, the 
milk dentition is in a degenerate condition. The milk 
teeth are present, but none become sufficiently developed 
to appear above the gums, except the last premolar, and 
in some cases the canine and the incisors. The sloths 
have only one set of teeth and are therefore Monophy- 
dont. Mammals having both a milk and a permanent 
set are termed Diphydont. 

In the majority of mammals the teeth are divided 
according to form and function into four groups : incisors, 
canines, premolars, and molars. Such a dentition is 
known as Heterodont, in distinction to the Homodont 
dentition, in which all the teeth have the same form, as 
is the case in the dolphins. In mammals with a hetero- 
dont dentition the number of teeth in the different genera 
varies considerably, as seen by the following formula : 



Pig, 

Dog, 

Cat, 

Porcupine, 
Sheep, . . 
Horse, . . 
Opossum, 



c 



P f, m 1 = 44 

p I, m I = 42 

c I, p I, m ± = 30 

c %, p j, m I = 20 

c f, P I, m f = 32 

c {, p f, m f = 44 

c {, p I m I = 50 

Man, if, c }, p f , m f = 32 

The elephant presents a very specialized dentition. It 
has no canines nor any lower incisors. The single pair 
of upper incisors is developed into long tusks, much 
prized for ivory. They continue to grow throughout 
the entire life of the animal. Six molars are present 
on each side, only one or two of which are functional at 



124 ELEMENTS OF MAMMALIAN ANATOMY. 

once. The posterior ones move forward to take the 
place of the anterior as these become worn out. The 
tusks of the walrus are its canines greatly developed. 
None of the typical modern Ruminants have incisors 
in the adult state, though they are present in the embryo. 
Palaeontology has demonstrated that the ancestors of 
the Ruminants had well-developed upper incisors in the 
later Eocene times. The occurrence of the rudimentary 
upper incisors in the embryo furnishes evidence of a full 
dentition in the ancestors of the ruminants, since the 
individual embryological history is somewhat of a 
recapitulation of the ancestral history of the race. 



THE PHARYNX. 

The pharynx is that portion of the alimentary canal 
between the mouth and the esophagus. The structure 
is well shown by making a sagittal section through the 
head and neck. This is best done with a saw, after the 
specimen is frozen by placing it out-of-doors during one 
or two days of cold winter weather. 

There are seven openings into the pharynx: the two 
posterior nares (Fig. 18), opening anteriorly from the 
roof; a Eustachian tube on each side; the esophagus; 
and the larynx, leading into the trachea. The mucous 
membrane lining the pharynx contains many simple 
microscopic mucous glands. 



VISCERA. 

The body cavity must be opened before the rest of the 
alimentary canal can be displayed. The entire ventral 
wall of the thoracic and abdominal cavities should be 
cut away with the bone forceps and scalpel. The body 



ORGANS OF DIGESTION. 1 25 

cavity is divided into two parts by the diaphragm (Fig. 
54). The cephalic portion, the thoracic cavity, contains 
the esophagus, heart, blood-vessels, thoracic duct, trachea, 
and lungs. In the young cat there is present also the 
thymus gland, stretching cephalad several centimeters 
from the base of the heart. The transparent membrane 
lining this cavity and investing the lungs is the pleura. 

The caudal part of the body cavity, or ccelom, is the 
abdominal cavity containing the abdominal viscera, 
which are here briefly described. The liver, a large 
brownish-red organ, is adjacent to the diaphragm on the 
right side, while the stomach (Fig. 54) lies close to the 
diaphragm on the left. The spleen is the dark red, flat, 
elongated organ caudad of the stomach on the left side. 
The sheet of thin transparent tissue more or less laden 
with fat, depending from the stomach and covering the 
intestines like an apron, is the greater omentum. It is 
a portion of the peritoneum which lines the abdominal 
cavity and invests most of the organs therein. The 
pancreas is a pinkish elongate body, bent at a right 
angle near its middle, so that one portion lies in the 
bend of the duodenum and the other dorsal to the stom- 
ach. The kidneys may be recognized by their well- 
known shape and dorsal location in the cephalic lumbar 
region. The ovaries are small pinkish bodies lying near 
the kidneys, adjacent to the dorsal abdominal wall. 
The uterus is easily known by its two horns extending 
caudad from the ovaries to their junction at the body 
of the uterus. The bladder, if full of urine, is at once 
recognized; and if empty, appears as a small pear- 
shaped mass ventrad to the rectum (Fig. 54). 



126 ELEMENTS OF MAMMALIAN ANATOMY. 

ESOPHAGUS. 

The esophagus or gullet is that portion of the ali- 
mentary canal leading from the pharynx to the stomach. 
In the thoracic cavity it lies dorsal to the heart (Fig. 54) 
by the side of the aorta. Immediately caudad of the 
diaphragm it opens into the cardiac end of the stomach 
(Fig. 58). 

STOMACH. 

The stomach is that dilated portion of the canal 
lying immediately caudad of the diaphragm on the left 
side. The esophageal end of the stomach is known as 
the cardiac portion, and the intestinal end is the pyloric 
portion (Fig. 58). Here a circular fold of mucous mem- 
brane embraced by a sphincter muscle serves as a valve 
to open and close the pylorus or gateway to the intes- 
tine. The dorsal surface of the stomach is its lesser 
curvature and the ventral convex surface is its greater 
curvature. The structure of the walls of the stomach 
is described below. 

INTESTINE. 

The intestine is that much contorted portion of the 
canal leading from the stomach to the external aperture 
or anus. The first portion, the small intestine (Fig. 58), 
is about three feet long in a large cat, and is less in 
diameter and much more convoluted than the second 
portion, or large intestine. 

The small intestine consists of three parts: the duo- 
denum, the jejunum, and the ileum. The duodenum is 
the first twelve or fifteen centimeters. A duct from the 
liver and the gall-bladder and two ducts from the pan- 
creas, empty into it. The former is the ductus com- 



ORGANS OF DIGESTION. 



127 



munis choledochus and the latter are the pancreatic 
ducts. The jejunum is the portion of the small intestine 
next to the duodenum. It is about twenty-five centi- 




Fig. 58. — Ventral Aspect of the Alimentary Canal with the Ileum 
Pulled to One Side. 

ac, Small intestine opening into the large intestine ; a, anus ; ao, ascending 
colon; bd, hepatic duct; ce, cecum; cd, cystic duct; cs, bile-cyst or 
gall-bladder;' cr, cardiac portion of the stomach; di, diaphragm; 
du, duodenum; do, caudal part of the descending colon; dc, ductus 
communis choledochus; gc, greater curvature of the stomach; il, 
ileum ; je, jejunum ; Ic, lesser curvature of the stomach ; 02, esophagus ; 
pn, pancreas; py, pyloric portion; pa, mesenteric gland; pd, pan- 
creatic duct; r, rectum; sp, spleen; tc, transverse colon. 



128 



ELEMENTS OF MAMMALIAN ANATOMY. 



meters long. No special mark indicates its limits. It 
is so called because that portion of the canal in man is 
frequently empty after death. The ileum constitutes 
more than two- thirds of the small intestine, is much 
convoluted, and extends from the jejunum to the large 
intestine on the right side of the abdominal cavity, near 
the iliac bone. The intestine is supported by the folds 

of the peritoneum known as 
the mesenteries. 

The large intestine con- 




Fig. 59. — Transverse Section of 
the Cat. 

i, Sections of the intestine ; d, duo- 
denum; a, aorta; pan, pancreas; 
pa, pancreas Aselli; spl, spleen; 
sp, spinous process of the lumbar 
vertebra ; tr, transverse process ; 
v, post-cava or inferior vena cava ; 
om, greater omentum ; the broken 
line is the peritoneum. 




Fig. 60. — Cross-section of the 
Cardiac End of the Stomach. 
X 3. 

cav, Cavity of the stomach ; ex, ex- 
ternal muscular coat ; in, internal 
muscular coat; m, mucous coat; 
mm, muscularis mucosae; s, sub- 
mucous or areolar coat ; se, serous 
or peritoneal coat. 



sists of the cecum, colon, and rectum. The cecum is the blind 
conical projection at the beginning of the large intestine. 
It is only one or two centimeters long. The ileum opens 
into the large intestine at the junction of the cecum and 
colon. An annular fold of mucous membrane, strengthened 
by a sphincter muscle, forms the ileocecal valve, which re- 



ORGANS OF DIGESTION. 



129 




i 






tains the food in the small intestine until the nutriment 
is absorbed (Fig. 58). 

The colon, extending from the cecum to the rectum, is 
composed of the ascending, trans- 
verse, and descending parts. The as- 
cending colon lies on the right side; 
the transverse extends crosswise, con- 
necting the ascending with the de- 
scending, which lies on the left side. 
The descending colon terminates in 
the rectum, which is five or six centi : 
meters long. 

The wall of the alimentary canal is 
composed of three chief coats — 
mucous, areolar, and muscular. These 
coats may be seen by cutting trans- 
versely, with a sharp scalpel, a portion 
of the stomach hardened in formalin. 
The mucous coat (Fig. 60) lines the 
lumen and contains the numerous 
glands which vary much in the differ- 
ent portions of the canal. The esopha- 
gus contains the esophageal glands, 
whose secretion probably has no other 
effect on the food than to facilitate its 
passage. The mucous coat of the 
stomach contains the gastric glands, 
which yield pepsin and hydrochloric 
acid, the chief agents of the gastric 
digestive fluid (Fig. 61). The glands 
in the cardiac end of the stomach 
differ from those in the pyloric end in containing numerous 
parietal or acid cells which probably secrete the hydro- 
. chloric acid for digestion. 




Fig. 61. — A Cross- 
section of the Mu- 
cous Coat of the 
Stomach between 
the Lines a and c in 
Fig. 60 shows Two 
Gastric Glands. X 
250. Diagrammatic 

a, Mouth of gastric 
gland ; e, columnar 
epithelial cells on 
the food surface of 
the stomach ; /, lu- 
men of a gland; o, 
oxyntic or acid cell. 



i;o 



ELEMENTS OF MAMMALIAN ANATOMY. 



The mucous coat of the small intestine contains tube- 
like glands, the glands of Lieberkiihn, whose secretion 



changes starch into 



In the duodenum and 




jejunum the mucous membrane is thrown into numerous 
transverse folds, valvuli conniientcs, which increase the 
surface for absorption. The villi are minute finger-like 
processes Fig. 62), barely apparent to the naked eye. 
projecting into the lumen for the purpose of absorbing 
the nutriment from the chyle. They consist of a covering 
of columnar epithelial cells (Fig. 
6 3 . within which ends a chyle ves- 
sel or lacteal surrounded by small 
blood-vessels held in place by con- 
nective tissue. The fatty portions 
of the food are carried by the lac- 
teals Fig. ;S I to the left thoracic 
duct, and thence to the jugular vein, 
while other portions of the food are 
taken up by the capillaries of the 
portal system, which begin in the 
villi Fig. 63). The mucous mem- 
brane of the large intestine like- 
wise contains tube-like glands sim- 
ilar to the glands of Lieberkiihn, 
but no villi. 
The submucous or areolar coat is adjacent to the mucous 
coat of the intestine, but in the stomach the muscularis 
mucosae intervenes. Xext to the submucous coat is 
the muscular coat, composed of two layers, one of circular 
fibers, the other of longitudinal fibers. An additional 
laver of oblique fibers is present in the cardiac end of 
the stomach, which aid in giving that organ the peculiar 
churning or peristaltic motion necessary for chymifica- 
tion of the food. A fourth coat or serous covering sur- 



Fig. 62 — Cross-sectilox 
of the Small Intes- 
tine. X 5. 

ex, Longitudinal muscular 
coat ; ik, circular muscu- 
lar coat; iru, mucous 
coat; lb, glands of Lie- 
berkjhn; se, serous or 
peritoneal coat; sm, 
submucous or areolar 
coat. 



ORGANS OF DIGESTION. 



I3 1 



rounds the muscular coat of the stomach and intestines. 
It is merely a reflected portion of the peritoneum which 
lines the entire abdominal cavity. 



THE ACCESSORY GLANDS OF DI- 
GESTION. 

The salivary glands are five in 
number on each side of the head. 
They secrete the saliva, certain 





Fig. 63. — A, Cross-section of the Mucous Coat of the Intestine 
between a and c, in Fig. 62. X 200. Diagrammatic. 

vil, Two villi projecting into the lumen of the intestine; ep, columnar 
epithelial cells; /, lacteal; a artery; v, vein; lb, gland of Lieberkiihn; 
m, mouth of gland of Lieberkiihn; ar, location of areolar or sub- 
mucous coat. 

B, Photomicrograph of Section of Intestine with Blood-vessels 

Injected. 
b, Large artery; mu, muscular coat; s, submucous or areolar coat. 



elements of which have the power of changing starch 
into sugar. 



132 



ELEMENTS OF MAMMALIAN ANATOMY. 



The parotid gland is the largest of the salivary group 
and lies just ventrad to the base of the external ear 
(Fig. 64) beneath the skin. It is about two centimeters 
in diameter. Its secretion is poured into the mouth 
through Stenson's duct, which may be seen extending 
from the cephalic margin of the gland over the masseter 
muscle, to near the angle of the mouth, where it per- 
forates the buccinator muscle, and opens within the 
mouth on the cheek, opposite the prominent cusp of the 

last premolar. The duct 
and gland may be injected 
with Berlin blue by insert- 
ing the cannula into the 
orifice of the duct (Fig. 64). 
The submaxillary gland is 
near the angle of the man- 
dible and ventrad to the 
parotid. Wharton's duct 
extends from its anterior 
surface, between the digas- 
tric and masseter muscles, 
to its orifice on the floor of 
the mouth, opposite the last 
tooth of the mandible. 
The sublingual gland is 
quite small, elongated, and lies cephalad of the submaxil- 
lary. Its duct extends parallel with that of the submaxil- 
lary and opens within the mouth upon the same papilla 
beneath the tongue. The malar gland is very small and 
lies near the angle of the mouth ventrad of Stenson's duct. 
Its several ducts, which are not easily demonstrated, pass 
through the cheek to open within the mouth. The zygo- 
matic or infraorbital gland lies on the lateral part of the 
orbit on the ventro-lateral surface of the eyeball. It may 




nr-cr 



Fig. 64. — Lateral Aspect of the 
Head with the Skin Removed. 

cr, Carotid artery ; es, esophagus ; Im, 
lymphatic gland; nr, vagus and 
sympathetic nerves ; sm, sub- 
maxillary gland; tr, trachea; v, 
cervical vertebra. 



ORGANS OF DIGESTION. 1 33 

be seen by cutting away the zygomatic arch and the mas- 
seter muscle. From near the ventral angle of the gland 
a duct leads to the roof of the mouth posterior to the 
molar tooth. 

The liver is the largest gland in the body and is situated 
immediately caudad of the diaphragm (Fig. 54), and in 
contact with the right lateral and cephalic surfaces of 
the stomach. It is composed of five lobes: the caudate, 
right lateral, right central, left central, and Spigelian. If 
the abdominal wall is removed, a ventral view of the 
liver shows the caudate lobe to be the most caudal part 
of the organ on the right side. Its dorsal surface is 
in contact with the kidney. Cephalad of this is the 
right lateral lobe in contact with the diaphragm. These 
two lobes are of about the same size. The right central 
lobe is much larger than the two preceding ones and 
presents a deep cleft in which is lodged the green gall- 
bladder or cyst. The left central lobe is small, lies in 
contact with the diaphragm, and is separated from the 
right central lobe by the broad or falciform ligament, 
which is a double layer of peritoneum, apparently pending 
from the diaphragm. The left lateral lobe is about the size 
of the right central lobe and is in contact with the dia- 
phragm, stomach, and right central lobe. The Spigelian 
lobe is seen by raising the liver from the stomach. It 
is the smallest lobe and lies adjacent to the esophagus. 

The right lateral fissure is between the right lateral 
and right central lobes. The cystic notch shelters the 
gall-bladder. The umbilical fissure is between the two 
central lobes. The round ligament lies in this fissure. 
The left lateral fissure is between the left central and 
left lateral lobes. The transverse fissure separates the 
ventral from the Spigelian lobe and lodges the portal 
vein, hepatic artery, and the main bile-ducts. 



134 ELEMENTS OF MAMMALIAN ANATOMY. 

The bile secreted by the liver passes through the 
several ducts from the various lobes, to the main hepatic 
duct, which may be seen by cutting away the liver from 
the right side of the gall-cyst, and carefully picking off 
the peritoneum ensheathing the vessels between the 
Spigelian lobe and the cystic duct. The latter is some- 
what convoluted in its course from the deeply imbedded 
end of the cyst, to a point on the duodenum about three 
centimeters from the pylorus. The main hepatic duct 




Fig. 65. — Photomicrograph of Section of the Liver. X 300 
b, Blood-vessel. 

joins the cystic duct (Fig. 58) near its middle. The 
common duct thus formed is the ductus communis 
choledochus. When the bile is secreted faster than it 
is permitted to enter the intestine, it passes backward 
from the ductus communis choledochus into the cyst. 

The bile aids in the absorption of the fats by the 
villi, and renders the chyme alkaline so that the pan- 
creatic juice may act more strongly. The formation of 
red blood-corpuscles takes place in the liver of the 



ORGANS OF DIGESTION. 1 35 

embryo, while in the adult the liver destroys these 
corpuscles. The chief function of this organ, however, 
is the formation of glycogen from the sugars and starches 
eaten and the gradual transformation of this glycogen 
into sugar as demanded for the nutrition of the body. 
Diabetes mellitus is caused by a diseased liver which 
permits sugar to accumulate in the blood. 

The pancreas (Fig. 58) is an elongated gland bent at 
a right angle near its middle. The body of it lies dorsal 
to the pyloric portion of the stomach, and the head lies 
close along the concavity of the duodenum. It has two 
ducts, one of which enters the duodenum in common 
with the ductus communis choledochus, while the other 
enters about three centimeters further caudad. The 
pancreatic juice acts on the starches, proteids, and fats. 



THE PERITONEUM. 

The peritoneum (Fig. 59) is the serous sac lining the 
abdominal cavity and investing most of the organs 
therein contained. The four portions of the peritoneum 
are known as the omenta, the mesenteries, parietes, and 
ligaments. The omenta are three in number, the largest 
of which is the great or gastrocolic omentum, stretching 
caudad from the dorsal abdominal wall and the greater 
curvature of the stomach, so as to cover the intestine 
like an apron. It is composed of four layers of peri- 
toneum forming a closed sac, and bearing more or less 
fat. Two layers form the ventral wall of the sac attached 
to the stomach, and two layers are also present in the 
dorsal wall of the sac which invests the pancreas. 

The lesser omentum, or gastrohepatic omentum, ex- 
tends caudad from the liver to the pyloric part of the 
stomach and duodenum. Its two folds extend from the 



136 ELEMENTS OF MAMMALIAN ANATOMY. 

two sides of the portal fissure, ensheathing the portal 
vein, hepatic artery, and cystic duct. The gastros picnic 
omentum stretches from the cardiac region of the stomach 
to the spleen, which it embraces, and then proceeds to 
the diaphragm. 

The mesenteries are the two layers of peritoneum 
suspending the intestine from the dorsal abdominal wall. 
There are four mesenteries: the true mesentery, sus- 
pending the jejunum and ileum; the mesoduodenum, 
suspending the duodenum; the mesocolon, suspending 
the colon; and the mesorectum, suspending the rectum. 

The parietes or parietal peritoneum is that portion 
lining the walls of the abdominal cavity. It is a closed 
sac in the male, but in the female the Fallopian tubes 
open into it. 

The ligaments are the layers of the peritoneum sus- 
pending other organs than parts of the alimentary 
canal. The falciform ligament extends from the caudal 
surface of the diaphragm and the abdominal wall, to 
the surface of the liver, which its line of attachment 
divides into halves. The round ligament is a fetal relic 
extending from the umbilicus to the longitudinal fissure 
on the caudal surface of the liver. A third ligament 
connects the dorsal border of the liver with the dia- 
phragm. The broad ligaments of the uterus are the folds 
of peritoneum which embrace the uterus, the Fallopian 
tubes, and the ovaries. The ovarian ligaments are short 
cords extending from the ends of the uterine cornua to 
the ovaries. The round ligaments of the uterus pass 
from the sides of the uterus to the brim of the pelvis. 

The peritoneum is called a serous membrane because 
of the colorless serum secreted by it. Other serous 
membranes are the pericardium of the heart, the pleura 
lining the thoracic cavity and investing the lungs, and 



ORGANS OF DIGESTION. 



137 



the synovial membranes of the joints. Serous mem- 
branes invest only such cavities as are not exposed to 
the air. All other cavities are lined by mucous mem- 
brane. A serous membrane consists of a layer of fibrous 
connective tissue covered by plate-like endothelial cells. 



REMARKS ON THE MAMMALIAN DIGESTIVE SYSTEM. 

The digestive system of mammals varies somewhat 

among the different groups. In carnivorous animals, as 

a rule, the alimentary canal is much shorter than in 




Fig. 66. — Diagram of the Stomach of a Ruminant. 
a, Dotted line showing the direction of the food in the process of diges- 
tion ; abom, abomasum ; du, duodenum ; ae, esophagus ; ps, psalterium ; 
rt. reticulum. 



herbivorous. In the wildcat the canal is four times the 
length of the body, while the canal of the sheep is twenty 
times as long as the body. In man it is about nine 
times as long as the distance from the crown of the 
head to the coccyx. In Ruminants, such as the cow and 
the sheep, the stomach is very large and divided into 
four chambers — the rumen or paunch, reticulum, psal- 
terium or many plies, and abomasum (Fig. 66). The 
rumen and reticulum serve as mere storage cavities, 
from which the food returns to the mouth for thorough 



138 ELEMENTS OF MAMMALIAN ANATOMY. 

mastication, and then passes direct, by means of a 
groove in the esophagus, into the psalterium, and finally 
on to the abomasum. The latter is the true stomach, 
and is provided with gastric glands. In the camels the 
rumen and reticulum have connected with them pouch- 
like diverticula for the storage of water. The con- 
stricted openings of the pouches into the rumen or 
reticulum may be entirely closed by sphincter muscles. 

In man and the higher apes there is present an at- 
tenuated extension of the cecum known as the vermi- 
form appendix. In the fetus of man it is proportionally 
longer than in the adult. In the herbivorous mammals, 
such as the cow and rabbit, the cecum is greatly enlarged, 
so as to play an important part in digestion. In a few 
forms, such as the sloths, some Cetacea, and a few 
Carnivora, the cecum is absent. 

The lowest mammals, the Monotremata, resemble 
birds and reptiles in possessing a cloaca into which open 
the rectum and the urinary and genital ducts. The cloaca 
opens externally beneath the tail. Salivary and thyroid 
glands, pancreas, and liver are present in all mammals, 
but the gall-cyst is absent in Cetacea, the Perissodactyla, 
Hyracoidea, and a few Rodentia. The liver is usually 
relatively larger in fat-eating animals. 



PRACTICAL QUESTIONS AND SUGGESTIONS. 

1. Describe the fauces. 

2. Describe in detail every feature visible on the dorsal surface of 
the tongue. 

3. Give the number of fangs in each tooth of the permanent set. 

4. Give the number of each kind of teeth in the two sets. 

5. Draw two aspects of the sectorial tooth. 

6. How thick is the enamel of the teeth? 

7. Name some mammals which do not have enamel on the teeth. 

8. Name some toothless mammals. 

9. Name some mammals having only one set of teeth. 



ORGANS OF DIGESTION. 1 39 

10. Give the dental formulae for three ungulates. 

11. In what animals are some of the teeth greatly enlarged ? 

12. Do any ruminants have upper incisors? 

13. Name the important features of the pharynx. 

14. Name every organ in the abdominal cavity, telling with what other 
organs it is in contact. 

15. Describe as much of the peritoneum as you can see in your specimen. 

16. Draw the alimentary canal in its natural position, showing all 
ducts leading into it, and label all parts. 

17. How much longer is the small intestine than the large one? 

18. On what does the length of the canal in different mammals largely 
depend? 

19. Make a section of a portion of the wall of the stomach and draw 
what is seen, labeling all parts. 

20. Make a section of the small intestine, draw what can be seen by 
naked eye or simple microscope. 

21. About how many villi to each square millimeter? 

22. Describe the two channels through which the food passes from 
the intestines to the heart. 

23. Make a somewhat diagrammatic drawing representing that part 
of the venous system conveying the food from the intestines to the heart. 

24. What is the size of the cecum in other mammals than the cat? 

25. Give the location, size, and form of the salivary glands 

26. Name the lobes of the liver in order of their size. 

27. How is the liver held in place? 

28. Draw the pancreas, showing ducts leading to the intestine. 

29. Draw the complex stomach characteristic of many ruminants. 

30. What is the cloaca and in what mammals is it present? 



THE VASCULAR SYSTEM. 

The vascular system is composed of the central forcing 
muscular organ, the heart; a system of vessels, the 
arteries, carrying the blood from the ventricles to the 
lungs and all parts of the body; a system of vessels, the 
veins, returning the blood to the auricles; and numerous 
microscopic vessels, the capillaries, connecting the 
termination of the arteries with the origin of the veins. 



THE HEART. 

The location of the heart in the cat may be seen by 
removing the ventral thoracic wall, but for the study 
of the parts, the heart of an ox or a sheep will be found 
more satisfactory. The heart of the cat lies between 
the lungs (Fig. 80) in the thoracic cavity a little to the 
left of the median line. The caudal end is the apex, and 
the cephalic end is the base. The entire organ is in- 
vested by a tough membrane, the pericardium, which 
when cut permits the pericardial fluid to run out. All 
the blood-vessels originate from the dorsocephalic aspect 
of the heart. 

It is composed of a right and left half, each of which 
consists of an auricle and a ventricle. The separation 
between the two halves is apparent on the ventral 
surface. The auricles receive the blood from the veins 
and pass it to the ventricles, which disperse it through 
the arteries. There is no aperture between the auricles 
or the ventricles. The aperture between the right 
auricle and the right ventricle is guarded by the tricuspid 

140 



THE VASCULAR SYSTEM. 



141 




valve which prevents the blood from returning into the 
auricle when the systole or contraction pushes the blood 
into the pulmonary artery. The opening between the 
left auricle and left ventricle 
is guarded by the bicuspid or 
mitral valve. These valves 
may be displayed by cut- 
ting away the caudal half of 
the ventral wall of the ven- 
tricles, when t*he chordae 
tendinese, delicate tendin- 
ous cords, will be seen ex- 
tending from the margins of 
the translucent membran- 
ous valves to the columnar 
carneae or muscular projec- 
tions on the walls of the 
ventricles. The walls of the 
auricles are thin in compari- 
son with the walls of the left 
ventricle, which are twice as 
thick as the walls of the 
right ventricle (Fig. 68). 

The auricles are very 
'small when not injected, 
and may by the beginner be 
cut away with the pericar- 
dium and surrounding adi- 
pose tissue. The right auri- 
cle receives three veins, the 
precava, postcava, and cor- 
onary veins, all of which enter its dorsal aspect. The por- 
tion of the auricle into which the above veins open is the 
sinus venosus. At the dorsal part of the septum which 



Fig. 67. — Heart Viewed Ven- 
trally, with ventrae haef of 
the auricees and ventricles 
Cut Away and the Auricles 
Drawn Later ad. Partly dia- 
grammatic. 

a, Orifice of the aorta ; ao, aorta ; 
aao, arch of the aorta; ap, orifice 
of the precava ; as, orifice of the 
postcava; Iv, left pulmonary 
veins; Ivn, left ventricle; mt, mi- 
tral or bicuspid valve; la, left 
auricle; p, orifice of the pulmon- 
ary veins ; pc, postcava ; pre, pre- 
cava ; ba, orifice of the pulmonary 
artery; prv, right pulmonary 
veins ; rv, right ventricle and one 
of the right pulmonary veins; ra, 
right auricle ; rp, right pulmonary 
artery; tr, tricuspid valve; xp, 
left pulmonary artery. 



142 



ELEMENTS Or MAMMALIAN ANATOMY 



divides this auricle from the adjoining one is an oval 
depression, the fossa ovalis, where, in the embrvo. the 
two auricles communicated. The left auricle is in con- 
tact with the right dOrsally, and receives three pulmonar\- 
veins (Fig. 69). 



ra. 




m 



Fig. 68. — Ventral Aspect of the 
Heart with its Caudal Third 
Cut off Transversely. 

a, Adipose tissue; be, brachioceph- 
alic artery ; la, left auricle ; lv, left 
ventricle; Ic, left carotid artery; 
o, ductus arteriosus ; pv, pulmon- 
ary vein; ba, pulmonary artery; 
pc, precava; psc, postcava; ra, 
right auricle ; re, right carotid ar- 
tery; rs, right subclavian artery: 
rv, right ventricle ; sb, left subcla- 
vian artery; tr, trachea. 




Fig. 69. — Dorsal Aspect of the 
Heart of the Cat. 

a Aorta ; ap, apex; as, azygos vein ; 
be, brachiocephalic artery; ca, 
coronary artery; cw, coronary 
vein ; /, left auricle ; le, left caro- 
tid artery ; Isb, left subclavian ar- 
tery ; p, postcava ; pc, precava ; pa . 
pulmonary artery dividing into 
its right and left branches ; ra , 
right auricle ; re, right carotid ; 
rs, right subclavian ; v, pulmonary 
veins. 



From the right ventricle arises the pulmonary artery 
which carries the impure blood to both lungs. Its 
mouth is guarded by three semilunar valves which 
prevent the return of the blood. The left ventricle gives 
origin to only one important vessel, the aorta, which 
arches dorsally around the left auricle, and at the apex 



THE VASCULAR SYSTEM. 1 43 

of the arch gives off two branches, the brachiocephalic 
or innominate, and the left subclavian. Three semilunar 
valves also guard the mouth of the aorta. The arteries 
of the heart may easily be distinguished from the veins 
by the fact that the walls of the former are much thicker. 



THE ARTERIES OF THE TRUNK. 

The blood-vessels form two systems of circulation; 
the one known as the pulmonary circulation includes the 
arteries carrying blood from the right ventricle to the 
lungs, and the veins returning the blood from the lungs 
to the left auricle; the other, known as the systemic 
circulation, includes the arteries conveying the blood 
from the left ventricle to all parts of the body, and the 
veins returning the blood to the right auricle. 

The main artery of the systemic circulation is the 
aorta, which, beginning in the left ventricle, arches 
dorsad to the heart and extends along the spinal column 
to the tail. That portion in the thoracic cavity is termed 
the thoracic aorta, while that portion in the abdominal 
cavity is the abdominal aorta. Three semilunar valves 
guard the mouth of the aorta at its opening from the 
ventricle, in order that the blood may not be forced 
back into the heart by the contraction of the muscular 
coat of the arteries. 

The branches of the thoracic aorta are as follows: the 
right and left coronaryi arising from the aorta immediately 
beyond its exit front the ventricle^ are distributed to 
the walls of the heart. From the arch of the aorta arise 
two large branches: first, the brachiocephalic, giving 
origin to the right subclavian supplying blood to the 
arm, and the right and left carotids supplying the head 
and neck; and, second, the left subclavian, supplying 



144 



ELEMENTS OF MAMMALIAN ANATOMY. 



the left arm, brain, and sternum (Fig. 70). Ten pairs 

of intercostal arteries supply the intercostal spaces. 

x muscles of the back, and the spinal cord. Two bronchial 

arteries go to the lung tissue. Two to four esophageal 

arteries are distributed to the 
esophagus. Two or three pairs 
of lumbar arteries pierce the 
muscles of the back. 

The abdominal aorta gives 
off the following branches : the 
coeliac axis, the superior mes- 
enteric, the adrenolumbalis, a 
pair of renal, a pair of genital, 
an inferior mesenteric, a pair 
of iliolumbar, seven or eight 
pairs of lumbar, a pair of ex- 
ternal iliacs, a pair of internal 
iliacs, and a caudal artery 
(Fig. 70). 

The coeliac axis is a large 
branch arising just caudad to 
the diaphragm and gives off 
the hepatic branch to the liver, 
pancreas, and duodenum, the 







S 



Fig. 70. — Chief Arteries of the 

Trunk, Ventral Aspect. 
or, Arch of the aorta ; be, brachioceph- 
alic ; cc, eaeliae axis; cd, caudal; t t 
coronary ; /, gastric ; gr, gastric ; gas, 
gastroduodenalis ; hp, hepatic ; hi, 
location of heart; ten, intercostal?; 
%c, external iliac ; H, internal iliac ; 
2/, iliolumbar; im, inferior mesen- 
teric ; Is, left subclavian ; lpl, left 
pulmonary; m, splenic ; o, splenic; r, right pulmonary; re, renal; sp, splenic 
trunk; im.i, superior mesenteric; ±m, spermatic or ovarian; r, adrenolum- 
bafis; 1,2, J, 4, 5, and 6, lumbar arteries. 



td 



THE VASCULAR SYSTEM. 1 45 

coronary to the stomach, and is continued as the splenic, 
supplying the stomach and the spleen. The phrenic artery, 
supplying the diaphragm, sometimes arises from the cceliac 
axis, but usually from the adrenolumbalis. 

The superior mesenteric is about the same size as the 
cceliac axis, and arises within one centimeter caudad. It 
sends branches to the pancreas and both intestines. The 
adrenolumbalis is a small branch on the left side dividing 
into the adrenal, phrenic, and muscular. The renal 
arteries supply the kidneys and usually the suprarenal 
bodies. The genital arteries are small, and arise from 
one to two centimeters caudad of the renal arteries. 
They pass obliquely caudad to the ovaries in the female, 
and the testes in the male. The inferior mesenteric is 
almost as large as the superior mesenteric. It is dis- 
tributed to the large intestine. The pair of iliolumbar 
arteries are small branches supplying the muscles of the 
iliac region. 

Four or five pairs of lumbar arteries are given off from 
the dorsal side of the aorta at regular intervals between 
the diaphragm and the origin of the external iliac arteries. 
They supply the muscles of the back and spinal cord. 
The external iliac arteries are the largest branches of the 
abdominal aorta and carry blood to the hind-limbs. The 
internal iliac arteries arise more than a centimeter caudad 
to the external iliacs and furnish blood to the pelvic 
viscera and the muscles of the innominate region. The 
caudal artery is the continuation of the aorta beyond the 
origin of the internal iliacs. It extends into the tail 
(Fig. 70). 

ARTERIES OF THE HEAD AND NECK. 

From the arch of the aorta arise the brachiocephalic 
and left subclavian, which supply the sternum, neck, 



146 



ELEMENTS OF MAMMALIAN ANATOMY. 



head, and anterior extremities with blood. The brachio- 
cephalic gives off the left carotid and then divides into 
the right carotid and right subclavian (Fig. 71). Some- 
times the two carotids arise as a single trunk from the 




a , 



Fig. 71. — Ventral Aspect of the Arteries of the Head and Neck 
The carotids with their branches have been drawn laterad. 
Internal maxillary; ac, anterior cerebellar; ce, median cerebral; cr, 
posterior cerebral; cp, posterior cerebellar; ex, carotid plexus, many 
of whose branches reunite into one, ex', which is cut off; ex, external 
carotid; em, external maxillary; inc, origin of internal carotid; inc', 
union of internal carotid with circle of Willis; ia, inferior alveolar; 
if, infraorbital; i, optic chiasma; li, lingual; mn, middle meningeal; 
ms, muscular; oc, occipital; ol, anterior cerebral; pi, palatine; pa, 
posterior auricular; s, anterior spinal; th, thyroid; x, hypophysis; 
1. 2. 3, 4, 5, and 6, canal in cervical vertebrae. 



THE VASCULAR SYSTEM. 1 47 

brachiocephalic, which is then continued as the right 
subclavian. In this case the common trunk of the ca- 
rotid usually bifurcates within one or two centimeters of 
its origin, forming the right common carotid and the 
left common carotid, lying on the respective sides of the 
trachea beneath the sternomastoid and the sternohyoid 
muscles. The vagus or tenth cranial nerve and the 
sympathetic trunk lie in the same sheath with the 
carotid (Fig. 64). 

Each carotid artery in the neck region gives off the 
following branches : a thyroid to the thyroid cartilage and 
gland, and a muscular to the muscles of the neck. At 
the base of the skull, about the middle of the bulla of 
the temporal bone, a slight enlargement of the vessel is 
seen, from which arises the very small internal carotid, 
leading through the foramen lacerum medius to the base 
of the brain, where it joins the circle of Willis. The con- 
tinuation of the common carotid is now known as the 
external carotid. This, after giving off a lingual branch 
to the tongue, an external maxillary branch to the lower 
jaw, a post- auricular branch, and a temporal branch, 
turns to pass along the mesal aspect of the mandible, 
where it is named the internal maxillary, whose main 
branches are the inferior alveolar, the middle meningeal 
supplying the dura mater, several branches to form the 
carotid plexus, a palatine, sphenopalatine, and infraor- 
bital. The latter is the direct continuation of the internal 
maxillary. It supplies the upper teeth, lower eyelid, 
parts of the nose, and upper lip. An ophthalmic branch, 
supplying structures in the orbit, may arise from the 
carotid plexus or the internal maxillary. 

The vertebral artery is the first branch given off by 
either subclavian. It proceeds dorsad and cephalad to 
the sixth cervical vertebra, whence it extends through 



I-4-O ELEMENTS OF MAMMALIAN ANATOMY. 

the vertebrarterial canal and foramen magnum, to a 
junction with its fellow in the median line on the ventral 
aspect of the medulla oblongata. The union of the two 
vertebral arteries forms the basilar artery, which, after 
giving off several branches to the medulla and cerebel- 
lum, divides cephalad of the pons Varolii, forming the 
circle of Willis around the infundibulum and the optic 
chiasma. The circle of Willis receives the internal ca- 
rotid and gives off several arteries to the cerebrum. In 
man the internal carotid is much larger proportionately 
than in the cat (Fig. 71). 



THE ARTERIES OF THE THORACIC LIMB. 

There is more or less variation in the branching of the 
arteries in the limbs. No two cats are found exactly 
alike as to their arteries or veins. The same is true of 
all other mammals. 

The subclavian artery, which on the right side springs 
from, or is merely a continuation of, the brachiocephalic, 
and on the left side arises from the arch of the aorta, 
supplies the forelimbs with blood (Figs. 71 and 72). 
When the subclavian reaches the armpit, it is called the 
axillary artery, and its continuation along the humerus 
is the brachial artery. A continuation of the same artery 
along the radius is the radial artery, furnishing a large 
part of the blood to the fingers. 

Four branches arise from the subclavian: the vertebral 
artery, extending to the brain through the vertebrarterial 
canal; the internal mammary artery, arising from the 
ventral side of the subclavian opposite the origin of the 
vertebral, and extending along the visceral surface of 
the sternum, and sometimes supplying the pericardium 
of the heart; the superior intercostal, arising near the 



THE VASCULAR SYSTEM. 



149 



vertebral artery and supplying the first and second 
intercostal spaces, the deep muscles of the back, and 
the serratus magnus; and the thyroid axis, extend- 
ing cephalad to supply some muscles of the neck and 
the lateral aspect of the scapula (Fig. 72). 

The axillary artery gives origin 
to three branches: the anterior 
thoracic, the long thoracic, and 
the circumflex. The anterior tho- 
racic supplies the pectoral mus- 
cles . The long thoracic is distr ib - 
uted chiefly to the latissimus 
dorsi. The circumflex artery is 
almost as large as the continua- 
tion of the axillary, which be- 
yond this point is called the bra- 
chial. The circumflex, about a 
centimeter from its origin, after 
giving off the subscapular, which 
is distributed mainly to struc- 
tures in the subscapular fossa, 
winds around the neck of the 




Fig. 72. — Arteries of the Forelimb. 
Ventrae Aspect. 

a, Digital artery ; an, anastomotica magna ; 
ac, anterior circumflex ; ai, anterior in- 
terosseous; ax, axillary; at, anterior 
thoracic; b, digital artery; be, brachio- 
cephalic; br, brachial; c, dorsal branch 
of the radial where it passes between the 
second and third metacarpals to the 

palmar side ; ex, circumflex ; is, superior intercostal ; Is, left subclavian ; 
It, long thoracic; m, branch to extensor muscles; nt, nutrient; pi, pos- 
terior interosseous; r, radial; rd, radial recurrent; sf, supracondyloid 
foramen of the humerus; spr, superior profunda; sb, subscapularis ; sp, 
suprascapularis ; st, sternal ; th, thyroid axis ; ul, ulnar ; ur, ulnar recur- 
rent ; vt, vertebral. 



150 ELEMENTS 01 MAMMALIAN ANATOMY. 

humerus to its distribution in the triceps and deltoid 
muscles. 

The brachial artery, in addition to several muscular 
branches, gives origin to the anterior circumflex, superior 
profunda, the nutrient, and anastomotica magna. The 
anterior circumflex supplies the biceps and head of the 
humerus. The superior profunda is distributed to the 
muscles on the caudal aspect of the humerus. The 
nutrient artery enters the nutrient foramen of the humerus. 
The anastomotica magna is the small branch supplying 
the convexity of the elbow. The brachial artery after 
passing through the supracondyloid foramen takes the 
name of radial. 

The radial artery, which lies deep beneath the flexor 
muscles on the caudal aspect of the proximal half of the 
radius (Fig. 72), becomes superficial along its distal half, 
where the vessel is covered by skin and fascia only. In 
the region of the wrist, it curves dorsad and then pierces 
between the second and third metacarpals to the palmar 
side, where it sends branches to each of the digits, and 
forms the palmar arch by anastomosing with the ulnar 
artery beneath the flexor muscles. In addition to a few 
small branches, the radial gives off the following: the 
radial recurrens, supplying the concavity of the elbow; 
the ulnar recurrens, supplying the convexity of the elbow; 
the posterior interosseous, passing caudad between the 
radius and the ulna to the extensor muscles; the anterior 
interosseous, passing along the cephalic side of the inter- 
osseous membrane; the ulnar, extending beneath the 
flexor muscles, which it supplies, to the palm, where it 
anastomoses with the radial to form the palmar arch; 
and the volar branch, supplying the superficial palmar 
region. The ulnar and anterior interosseous frequently 
arise from the same trunk, as shown in the figure. The 



THE VASCULAR SYSTEM. 151 

ulnar artery in the cat is so small that it is frequently 
not filled by the starch injection, but in man it is larger 
than the radial. 



THE ARTERIES OF THE HIND-LIMB. 

As in the forelimb, the branching of the arteries in the 
hind-limb varies considerably in different specimens. 
The main artery of the leg lies on the ventral or mesal 
aspect of the femur, passing obliquely to the caudal side 
of the knee-joint, where it divides into two branches (Fig. 
73), one extending along the cephalic, the other along 
the caudal aspect of the crus. The cat, or at least the^ 
caudal half of a cat, should be fastened to the dissecti^f- 
tray on its back, the abdominal wall removed, and the 
viscera pushed laterad to demonstrate the origin of the 
artery of this limb. As in the forelimb, the main artery 
in different portions of the leg takes the name of the 
corresponding region. 

The external iliac is the largest artery arising from the 
aorta in the lumbar region. It gives off but one im- 
portant branch, the profunda, which, extending caudad, 
soon gives off a large epigastric artery to the abdominal 
wall, then smaller branches to the external genital 
organs, and numerous branches to the muscles on the 
caudal aspect of the femur. 

The femoral artery, which is a continuation of the 
external iliac, extends along the mesal aspect of the 
femur. In the proximal half of its course it is quite 
superficial, but the distal portion is covered by the 
gracilis, sartorius, and semimembranosus muscles. It 
furnishes four important branches: the anterior femoral, 
supplying mainly the quadriceps extensor muscle; the 
superior posterior femoral, supplying the adductor and 



152 



ELEMENTS OF MAMMALIAN ANATOMY. 



hamstring muscles; the saphenous, accompanying the 
saphenous nerve and vein to the foot, where it branches 
and anastomoses with the plantar artery; and the pos- 
terior inferior femoral, supplying mainly the gastrocne- 
mius group of muscles (Fig. 52). 

The popliteal artery is the continuation of the femoral 




Fig. 73. — Arteries of the Right Leg. Ventral Aspect. 
a, Aorta ; at, anterior tibial ; af, anterior femoral ; cd, caudal ; eg, epigastric ; 
em, external malleolar; fern, femoral; im, internal malleolar; il, ex- 
ternal iliac ; it, internal iliac ; lu, iliolumbar ; m, digital ; n, digital ; 
o, digital; p, peroneal; pa, profunda; pf, posterior superior femoral; 
pi, posterior inferior femoral ; pn, plantar ; pp, popliteal ; pt, posterior 
tibial; ps, saphenous. 



artery in the popliteal region on the caudal aspect of 
the knee-joint. One or two articular branches are given 
off here to the joint, in addition to the posterior tibial, 
which supplies the deep muscles of the crus. 

The anterior tibial artery is the continuation of the pop- 
liteal on the lateral cephalic aspect of the tibia, adjacent 



THE VASCULAR SYSTEM. 



153 



to the bone. By separating the tibialis anticus and ex- 
tensor longus digit or um muscles, this artery is well 
displayed. Near the knee-joint a small branch, the 
peroneal, is given off, and passes to the dorsal aspect 
of the foot, where it anas- 
tomoses with the dorsal 
branch of the saphenous, 
forming a superficial arch 
sending branches to the dig- 
its. The peroneal is so small 
that it is frequently not in- 
j ec ted . In the tarsal region 
two branches, an external 
malleolar and an internal 
malleolar, are given off. A 
centimeter or two distal to 
the latter branch, the main 
artery passes between the 
second and third metatar- 
sals to the deep plantar re- 
gion, where it receives an 
anastomosing branch from 

the saphenous, and sends , 

„ A , , ... Fig. 74. — Cross-section of Ar- 

off branches to the digits. tery and Vein, x 350. 

V, Vein; A, artery; en, inner coat; 

ep, epithelium lining the vessels ; 

et, middle or muscular coat of 
THE VENOUS SYSTEM. ve * n J ex > muscular coat of artery ; 

fb, fibro-areolar coat. — (From 
The veins are the vessels Martin's " Human Body.") 

returning the blood to the 

heart. As a rule, veins carry only impure blood, but 
the pulmonary veins returning blood from the lungs to 
the left auricle carry pure blood. After death the veins 
can readily be distinguished from the arteries by the 
fact that they have much thinner walls than the arteries 
13 




154 



ELEMENTS OF MAMMALIAN ANATOMY. 



and are usually full of blood, while the arteries are 
empty (Fig. 74). This is due to the fact that the thick 
muscular coat of the arteries, by its contraction tends 
to drive the blood into the veins, whose muscular coat 
is very thin. The three coats composing the walls of 
the veins are the epithelial, or tunica intima; the middle, 
or muscular; and the tunica adventitia, or outer elastic 
coat of fibro-areolar tissue. The veins of the central ner- 
vous system and its membranes have no muscular coat. 
While the only valves in the arteries are found at their 
• origin from the heart, the veins of the 
limbs, neck, and head possess numerous 
valves. These valves are formed by 
semilunar folds of the epithelial coat, 
strengthened bv fibrous tissue (Fig. 

75). 

The main deep veins of the limbs ac- 
company the arteries and take the same 
names as the arteries. A superficial set 
of veins is present also in the limbs. The 
large superficial vein on the lateral aspect 
of the forelimb is the cephalic. The 
superficial vein extending along the 
mesal aspect of the hind-limb is the 
saphenous. 
The Veins of the Trunk, Head, and Neck. — There are 
two chief venous trunks: the precava, or superior vena 
cava, and the postcava, or inferior vena cava. Both vessels 
open into the dorsal aspect of the right ventricle. The 
veins received by the postcava are thirteen in number. 
The phrenic veins collect the blood from the diaphragm 
and empty into the vena cava immediately caudad of 
the diaphragm. The several hepatic veins collect the 
blood from the liver, which must be partly dissected 




Fig. 75. — Vein Cut 
Open. Arrow 
shows the Di- 
rection of the 
Blood. 

v, Semilunar valves ; 
i, free edge of the 
valve. 



THE VASCULAR SYSTEM. 



3 55 



away to see their en- 
trance into the vena cava. 
The two suprarenal veins 
return the blood from the 
suprarenal bodies and 
two renal veins carry the 
blood from the kidneys. 
The left ovarian or sper- 
matic vein is a tributary 
to the left renal, but the 
right ovarian empties 
directly into the vena 
cava. A pair of small 
iliolumbar veins collect- 
ing blood from the lum- 

Fig. 76. — Ventral View of the 
Chief Veins of the Trunk, 
Neck, and Head. 

az, Azygos; au, anterior auricu- 
lar ; br, ' brachiocephalic ; cd, 
caudal ; cph, cephalic ; em, ex- 
ternal maxillary; ex, external 
jugular; eic, external iliac ; hp, 
hepatic; im, internal maxil- 
lary ; ij, internal jugular ; ims, 
inferior mesenteric; Urn, ilio- 

- lumbar ; ilc, common iliac ; iic, 
internal iliac; na, nasal; ov, 
ovarian or spermatic; pan, 
posterior auricular; pd, pan- 
creato-duodenalis ; pcv, prer 
cava; pst, postcava; prt, por- 
tal; phrn, phrenic; rn, renal; 
ste, superficial temporal; st, 
gastro - epiploica and coro- 
nary; sr, suprarenal; sir, ster- 
nal ; sp, gastrosplenic ; sm, su- 
perior mesenteric; sbcl, sub- 
clavian ; tr, transverse ; tg, lin- 
gual; vtr, vertebral; 1, 2, 3, 4, 
5, 6, the vertebrarterial canal 
of the first six cervical verte- 
brae; w, intercostals ; x, supe- 
rior intercostals. 




156 ELEMENTS OF MAMMALIAN ANATOMY. 

bar muscles empty into the vena cava a centimeter or more 
cephalad to the large common iliacs. The union of the com- 
mon iliac veins collecting the blood from the hind-limbs and' 
the pelvic region, and the caudal vein, forms the begin- 
ning of the postcava. The common iliac is formed by 
the union of the external and internal iliac veins in the 
pelvis. The former is much the larger of the two. 

The portal system begins with the veins collecting the 
blood from the intestines, pancreas, spleen, and stomach, 
and terminates where the hepatic veins enter the vena 
cava. The inferior mesenteric vein collects the blood 
from the large intestine ; the superior mesenteric, from the 
small intestines; the gastro splenic, from the spleen, 
stomach, and pancreas; the coronary, from the lesser 
curvature of the stomach; the gastro-epiploica, from the 
greater curvature of the stomach; and the pancreato- 
duodenal, from the pancreas and duodenum. The last 
three may empty directly into the portal vein or into 
one of the three branches first named (Fig. 76). 

The superior vena cava extends from the union of the 
brachiocephalic veins to the right auricle. Three im- 
portant veins empty into the precava: the azygos, col- 
lecting blood from the intercostal spaces; the sternal, 
lying on the visceral surface of the sternum; and the 
right vertebral, which, with its fellow, collects the blood 
from the deep muscles and spinal cord in the region of 
the atlas, and after making a strong anastomosis with 
the internal jugular vein, descends in company with the 
vertebral artery through the vertebrarterial canal of the 
first six cervical vertebrae. The left vertebral vein is a 
tributary of the left brachiocephalic (Fig. 76). 

The brachiocephalic vein is formed by the union of the 
subclavian and the external jugular. Sometimes the ver- 
tebral vein joins also in the union instead of emptying 



THE VASCULAR SYSTEM. 1 57 

into the precava. The subclavian vein returns the blood 
from the arm, and accompanies the subclavian artery. 
The external jugular veins are large vessels lying on either 
side of the neck beneath the platysma myoides muscle. 
When the skin is removed, the veins are plainly seen 
through this very thin muscle. The external jugular is 
formed ventral to the angle of the mandible by the 
union of the internal and external maxillary veins. The 
external maxillaries are united by a large transverse vein. 
The two tributaries of the external jugular are the 
cephalic and the internal jugular. The former is the 
superficial vein on the lateral aspect of the arm, and 
the latter is the small vein returning blood from the 
brain. 

A system of tube-like spaces, called sinuses, whose 
walls are formed by the dura mater lined with epithelium, 
takes the place of the large venous trunks within the 
cranial cavity. These sinuses are usually not filled by a 
starch injection, but may be filled by a gelatin mass. 
They cannot be dissected by the beginner. The superior 
longitudinal sinus extends in the median line beneath the 
roof of the skull, from the ethmoid region to the tentorium 
cerebelli, where it bifurcates to form the lateral sinuses; 
which proceed laterad and ventrad in the substance of 
the tentorium. The lateral sinus emerges from the ten- 
torium just caudad to the petrosal bone, where it follows 
the groove to the jugular foramen. This groove may be 
seen in a bisected or unroofed skull. 

The superior petrosal sinus lies in the angle formed 
by the junction of the tentorium and the petrosal bone, 
and unites with the lateral sinus just before it reaches 
the jugular foramen. The inferior petrosal sinus, col- 
lecting blood from the base of the brain, lies in the 
groove ventral to the petrosal bone, and unites with the 



i58 



ELEMENTS OE MAMMALIAN ANATOMY. 



lateral sinus at the jugular foramen. The union of these 
sinuses at this foramen forms the internal jugular vein, 
which extends deep beneath the muscles of the neck 




r.r *j 



spm 



sbi 



im 

spm 



ca 




r.r 1 



Fig. 77. — A, Ventral View of Heart axd Main Arteries in the Trunk 
of the Rabbit. B, Arteries of Man. 

a, Right auricle; ca, left carotid; c ax, ccEliac axis; i ??, innominate or 
brachiocephalic; il, common iliac; i m, inferior mesenteric; / r, left 
renal; r r, right renal; re, right intercostals ; sm, superior mesen- 
teric; spm, spermatic; sa, sacral; sb, left subclavian. 



with the carotid artery. It joins the external jugular 
opposite the shoulder- joint. At the base of the skull the 
internal jugular gives off a large transverse anastomosing 



THE VASCULAR SYSTEM. 1 59 

vein to the vertebral, so that the blood from the vein 
may return partly by the latter vessel. 

The pulmonary veins convey the pure blood from the 
lungs to the left auricle. There are three main trunks 
from each lung. These six veins are arranged in pairs 
(Fig. 69), constituting a left pair from the left lung; a 
median pair, composed of one branch from the right and 
one from the left lung; and a right pair from the right 
lung. Each pair forms a common trunk before entering 
the auricle. In order to demonstrate these veins one 
must remove the heart and lungs from an injected cat, 
and carefully dissect away the fatty and connective 
tissues enveloping the vessels. 

The peripheral connection between the arteries and 
veins is by means of capillaries, which are microscopic 
vessels with an extremely thin wall composed of a single 
layer of epithelial cells. These capillaries are so abun- 
dant everywhere in the flesh that a needle cannot be 
inserted without penetrating some. They form a kind of 
mesh or network, so that every cell may be supplied 
with oxygen and food and discharge its waste matter. 
All the blood carried to any portion of the body by the 
arteries is not returned by the veins, as a considerable 
amount of the plasma and some of the white corpuscles 
escape through the thin capillary walls and are returned 
to the circulation by a system of vessels called lymphatics 
(Fig. 78). 

PRACTICAL QUESTIONS AND SUGGESTIONS. 

1. What holds the heart in place? 

2. Draw the ventral aspect of the heart with the pericardium re- 
moved and label all features. 

3. When the heart is detached from the body, how do you distin- 
guish the dorsal from the ventral aspect? 

4. How many veins open into each auricle? 

5. What arteries lead from each ventricle? 



l6o ELEMENTS OF MAMMALIAN ANATOMY. 

6. After dissecting write a detailed description of the valves of the 
heart. 

7. Describe the differences in the appearance of the walls of the aorta 
and vena cava. 

8. From your dissection write a description of the features seen in 
each cavity of the heart. 

9. Name the branches of the thoracic aorta in order. 

10. Name the branches of the abdominal aorta and tell what organs 
each supplies. 

11. Draw the cceliac axis and its branches throughout their course 
and label all parts. 

12. Show by a drawing the relations of the aorta and venae cavse 
throughout. 

13. Make a diagrammatic cross-section of the neck, showing location 
of arteries and veins 

14. Describe the three routes by which blood may reach the brain 
and the two routes by which it may be returned to the heart. 

1 5 Name the arteries arising from the arch of the aorta. 

16. Draw the inner or mesal aspect of your dissection of the arteries 
of the thoracic limb and label all parts. 

17. Draw a ss-section of arm at middle of humerus to show location 
of main artery and vein. 

18. Draw cross-section of the middle region of the forearm to show 
location of chief arteries. 

19. Draw outline of the bones of the nianus and show relation of ar- 
teries to bones as seen from palmar aspect. 

20. Draw outline of femur and show course of main artery in relation 
to the bone as seen from mesal aspect. 

21. Draw outline of bones of the pes and show relations of the arteries 
to the bones as seen from the plantar aspect. 

2 _ At what joints in its course is the chief artery of the pelvic limb 
uperficial? 

23. Describe the difference in structure of a vein and an artery. 

24. What veins open into each auricle of the heart? 

1 : Name the veins returning the blood from each organ of the ab- 
dominal cavity. 

26. Draw the portal system and label all vessels 

2 1 Describe the veins returning the blood from the head. 

28. Describe the chief blood sinuses in the skull. 

29. Where are the valves found in the blood-vessels? 

30. If the brachial vein were cut, how could the blood from the manus 
reach the heart? 



THE VASCULAR SYSTEM. l6l 

THE LYMPHATIC SYSTEM. 

The lymphatics constitute that part of the vascular 
system which collects the colorless fluid called lymph 
from the tissues, and the chyle from the small intestine, 
and conveys them to the external jugular veins. The 
portion of the lymphatic system originating in the villi 
of the small intestine and conveying the chyle to the 
left thoracic duct is known as the lacteals. 

The lymphatic system consists of four parts: (i) the 
lymphatic spaces between the skin and muscles in all 
parts of the body, the spaces between the muscles adjacent 
to the bones, and internal spaces such as those enclosed 
by the peritoneum and pleura; (2) minute thin-walled 
vessels beginning by capillary mouths in the spaces just 
described and leading to larger vessels which empty into 
the tracheal trunks or thoracic duct ; (3) the glands, which 
vary in size from a mustard-seed to two centimeters in 
diameter, and are located chiefly on the side of the neck, in 
the axillary region, at the bifurcation of the trachea; in 
the inguinal region, lumbar region, and mesentery; (4) 
the two tracheal trunks and thoracic duct (Fig. 78). 

One of the largest of the lymphatic spaces is the 
greater cavity of the peritoneum. The cavity of the 
lesser peritoneum, a large lymphatic space, may be 
shown by separating the layers of the great omentum 
carefully. The cavity of the pleura within the chest is 
also a large lymphatic space. Numerous small lymph 
spaces are present in all parts of the body. The lym- 
phatic capillaries originating in these spaces are invisible 
to the naked eye, but their union into larger vessels may 
be demonstrated satisfactorily in a cat just killed, by 
pulling forward the tongue, and injecting very slowly 
beneath the skin, on its ventral aspect, five or ten centi- 



1 62 ELEMENTS OF MAMMALIAN ANATOMY. 

meters of a two per cent, solution of Berlin blue in warm 
water. 

The lymph glands (Fig. 78) of the cat are not nearly 
so numerous as in man. The largest lymph gland is 
the pancreas Aselli in the mesentery. It is considerably 
flattened and about two centimeters long. A few other 
very small lymphatic glands are also present in the 
mesentery. The two largest lymph glands of the head 
are just beneath the skin cephalad of the submaxillary 
gland. On the side of the neck beneath the cephalo- 
humeral muscle are three large lymph glands at the 
cephalic border of the scapula. A small axillary gland 
lies on the caudal side of the axillary vein beneath the 
scapula. A single popliteal gland is in the popliteal 
space, an inguinal gland lies on each side of the penis, 
two or three iliac glands are near the origin of the 
femoral artery, and a few small lumbar glands lie in 
the lumbar region of the abdominal cavity. 

All parts of the body have communication with the 
lymphatic vessels, which for the most part are so small 
as to be invisible unless injected, when they are easily 
recognized by their beaded appearance caused by the 
numerous valves within them. There are two systems 
of vessels in the head and extremities — the superficial 
and the deep. The former accompany mainly the super- 
ficial veins, and the latter follow the deep veins. On the 
outer aspect of the thoracic limb just beneath the skin 
two vessels are present, which flow into the cervical 
glands. They carry the lymph from the ball of the foot 
and the skin of the foot and forearm. One or two deep 
lymph-vessels are found accompanying the brachial vein 
and artery, which convey the lymph from the bones and 
muscles of the arm to the axillary gland. 

In the pelvic limb two or three superficial vessels are 



THE VASCULAR SYSTEM. 



163 



present transmitting the lymph from the foot to the 
popliteal gland, whence two ves- 
sels proceed to the deep lympha- 
tic system. The lymph from the 
bones and muscles of the leg 
reaches the iliac glands through 
two or three deep vessels lying 
near the femoral vein and artery. 
The inguinal glands receive most 
of the lymph from the skin of 
the leg. 

The lymph from the superfi- 
cial parts of the head flows 
largely into the submaxillary 
glands, while that from the brain, 
tongue, esophagus, and larynx 
empties into the laryngeal 
glands. 

The lymph of the right fore- 
limb, right side of the neck and 



Fig. 78. — Ventral Aspect of Chief 
Lymphatic Vessels of the Cat. 



a, Axillary gland ; as, pancreas Aselli ; an, 
superficial lymphatics from the head; 
b, bronchial glands receiving lymph 
from lungs ; c, lymphatic trunk ; cr, cer- 
vical glands; cv, laryngeal glands; d, 
vessel from diaphragm ; ej, external jug- 
ular vein; in, inguinal glands; il, iliac 
glands; ju, junction of thoracic duct 
with tracheal trunk ; I, lumbar glands ; 
li, large intestine ; Iv, lymph-vessel from 
liver; m, lacteal vessel and glands of 
mesentery; n, superficial lymphatics 
from limb ; o, deep lymph-vessels from 
limb ; on, lymphatics from thoracic wall ; 
ol, vessel from abdominal wall; oc, ves- 
sels from limb ; rec, receptaculum chyli ; 
s, subclavian vein; t, lymphatics from 

skin of leg ; tr, tl, tracheal trunks ; va, lymph trunk from pancreas Aselli 
to thoracic duct; v, precava; 1 and 2, submaxillary lymph glands. 




i6 4 



ELEMENTS OF MAMMALIAN ANATOMY. 



head, and right side of the thoracic wall is received by 
the right tracheal trunk. The left tracheal trunk re- 
ceives the lymph from the left side of the head, neck 
and thoracic wall, and the left forelimb. The thoracic 




Fig. 79. — Photograph of Lymphatic Capillaries Injected with 
Berlin Blue. They lie immediateh' beneath the skin on the outer 
aspect of the ear. 

a, Point of injection; the black area is Berlin blue lying in the connec- 
tive-tissue spaces from which the capillaries arise; n, injection escaped 
from ruptured vessel. 



duct receives the lymph from the lungs, heart, all the 
abdominal viscera, and muscles, and the hind-limbs. 
With but few exceptions, all the main lymphatic vessels 
pass through lymphatic glands before reaching one of the 



THE VASCULAR SYSTEM. 1 65 

three main trunks. In fact, the vessels bringing the 
lymph to the glands may be said to terminate there. 
They are called afferent lymphatics. The lymph moves 
free through the tissue of the gland, and on the opposite 
side is taken up by the efferent lymphatics. 

The right and left tracheal trunks lie on their respective 
sides of the trachea and empty into the external jugular 
vein just before its junction with the subclavian. The 
opening is guarded by a valve which prevents the blood 
from entering the lymphatic trunk. 

The thoracic duct (Fig. 78) is the largest vessel of the 
lymphatic system, but is usually invisible unless injected. 
It extends from the region of the kidneys on the dorsal 
aspect of the body cavity, along the left side of the 
spinal column, to its opening into the external jugular 
vein near where the latter joins the subclavian vein. 
The caudal end of the thoracic duct is expanded, forming 
the receptaculum chyli. Numerous valves are present 
in the duct, and give to it a moniliform appearance. It 
receives all the lymph from the left abdominal wall, both 
pelvic extremities, a large part of the thoracic wall, and 
the thoracic and abdominal viscera. 



DUCTLESS GLANDS. 

The spleen, thyroid gland, thymus gland, and suprarenal 
bodies are ductless glands whose functions are imper- 
fectly known. The largest of these is the spleen, which 
is of a deep red color in a fresh specimen, and lies in 
the abdominal cavity on the left side caudad to the 
stomach (Fig. 54). It is about five centimeters long, 
two centimeters wide, and less than a centimeter thick. 
It is composed of lymphoid tissue of two forms, sup- 
ported by connective-tissue trabecular which are merely 



1 66 ELEMENTS OF MAMMALIAN ANATOMY. 

prolongations of the enveloping capsule. The two 
forms of tissue can be seen by cutting the organ trans- 
versely. The dense lymphoid tissue appears as white 
spots less than the size of a pin-head. They are the 
Malpighian corpuscles. The intervening looser lymphoid 
tissue forms the greater part of the spleen, and is 
known as the splenic pulp. The splenic artery, a branch 
of the coeliac axis, enters the spleen at its hilus and 
divides into capillaries which terminate in irregular 
spaces, thus permitting the blood to flow freely through 
the splenic pulp, whence it is taken up by the capil- 
laries of the splenic vein leading to the portal vein. In 
embryonic life the spleen forms blood-corpuscles, but in 
postnatal life it seems to destroy blood-corpuscles. An 
animal from which the spleen has been removed may 
live many years in good health. 

The thyroid gland is composed of two parts lying on 
the lateral aspects of the trachea, just caudad to the 
larynx. Each part is less than two centimeters long. 
The two parts are sometimes connected by a small isth- 
mus extending ventrally across the trachea, as in man. 
An enlargement of this gland in man is called goiter. 
An animal can live only a short time after the removal 
of the thyroid unless it is fed thyroids or an extract 
of thyroid gland. The function of the gland is to supply 
iodin compounds to the system. 

The thymus gland is a median structure varying in 
size according to age. In a cat about one-third grown 
it is very large, extending cephalad from the heart along 
the ventral aspect of the trachea three or four centi- 
meters. As the cat grows older, it gradually dwindles, 
and is entirely absent in aged specimens. Its function is 
unknown. It persists throughout life in the lower ver- 
tebrates. 



THE VASCULAR SYSTEM. 1 67 

The suprarenal bodies are small, somewhat bean-shaped 
organs lying cephalad to the kidneys. An animal from 
which they have been removed can live but a short 
time. Their function is not known. They are sometimes 
spoken of as suprarenal capsules. 

The above-named ductless glands occur in all mammals 
in the same relative ocations. The anatomy of the 
lymphatic system is also exceedingly similar throughout 
the various orders of mammals. In some animals, espe- 
cially man, the lymphatic glands are more numerous than 
in the cat. The tracheal trunks are also wanting in man 
and a right thoracic duct about two centimeters long is 
usually present. A failure of the lymphatics to do their 
work results in dropsy. 

PRACTICAL QUESTIONS AND SUGGESTIONS. 

1. Which of the four parts of the lymphatic system are visible in 
your specimen? 

2. Describe size and number of lymphatic glands in the mesentery. 

3. Describe the location of lymph glands present in any other portion 
of your specimen. 

4. How do you distinguish a lymph gland from other glands? 

5. What causes the lymph to flow in one direction only? 

6. What is meant by afferent and efferent lymphatics? 

7. Which kind of blood-corpuscles are found within the lymph-vessels? 

8. From what regions does the thoracic duct receive the lymph? 

9. W r hat glands receive the lymph from the thoracic limb? 

10. What glands receive the lymph from the pelvic limb? 

11. Describe location of spleen, thyroid and thymus glands, and 
suprarenal capsules by naming the organs with which they are in contact. 

12. Draw a cross-section of the spleen and label all features visible. 

13. Draw a cross-section of the suprarenal body and label parts. 

14. Tell what you know of the functions of the ductless glands. 

15. What is a gland? 



THE RESPIRATORY SYSTEM. 

Respiration is the process whereby the tissues are sup- 
plied with oxygen and relieved of their carbon dioxid. In 
mammals, the special organs of respiration are the lungs, 
wherein the carbon dioxid is received from the blood, 
while at the same time the oxygen of the air passes 
through the thin-walled capillaries to the red blood- 
corpuscles capable of conveying it to the cells throughout 
the body. Each cell is composed largely of carbon, 
hydrogen, oxygen, and nitrogen, and any activity on the 
part of the cell is the result of the chemical union of 
some of its elements, whereby several waste products are 
formed, one of which is the gas, CO, ('carbon dioxid). 
This gas is a poison and therefore must be eliminated. 
It passes through the thin walls of the capillaries adjacent 
to every cell, and is transferred through the veins to the 
heart and thence to the lungs. Here the pulmonary 
artery divides up into capillaries ramifying over the air 
sacs (Fig. 82), thus permitting the carbon dioxid to 
escape into the air sacs. Other waste products resulting 
from chemical activity within the cells are carried away 
by the kidneys and sweat glands. 

The respiratory system consists of the nasal passages, 
pharynx, larynx, trachea, and lungs. The air taken in at 
the anterior nares is warmed in passing over the mucous 
membrane of the turbinated bones, after which it goes 
on through the posterior nares (Fig. 18) to the pharynx. 
and thence into the larynx. 

The larynx is the cartilaginous expansion of the cephalic 

168 



THE RESPIRATORY SYSTEM. 1 69 

end of the trachea, at the base of the tongue. The basi- 
hyal bone is attached to the cephalic ventral margin of 
the larynx and on each side is a thyrohyal bone (Fig. 20). 
Dorsal to the larynx is the esophagus. By removing 
carefully the muscles and fibrous tissue from the cartilage 
the larynx is seen to be composed of five pieces: the 
epiglottis, thyroid cartilage, two arytenoid cartilages, and 
the cricoid cartilage (Fig. 20). The epiglottis is the 
small triangular cartilage that closes the glottis when 
food passes into the esophagus (Fig. 55). The thyroid 
cartilage constitutes the largest part of the larynx. In 
man it forms the prominence known as Adam's apple. 
Dorsally the two halves of the thyroid cartilage are 
separated, each projecting cephalad into a process known 
as a cornu. The arytenoid cartilages are the two small 
paired pieces caudad to the thyroid, on the dorsal side. 
The cricoid cartilage forms a complete ring at the caudal 
end of the larynx (Fig. 20). 

There are a number of ligaments connecting the various 
parts of the larynx, the most important of which are the 
vocal cords. These are of two kinds — true and false. 
They are best demonstrated by dividing the larynx 
sagittally. The superior or false vocal cords are the two 
superior thyro-arytenoid ligaments passing from the 
arytenoid to the thyroid cartilage, at the base of the 
epiglottis. The cat is said to use these cords in purring. 
The inferior or true vocal cords are the inferior thyro- 
arytenoid ligaments, consisting, as in man, of a fold of 
mucous membrane on either side, just caudad to the 
false vocal cords (Fig. 55). The depression on either side 
between the true and false vocal cords is the ventricle. 
By means of the muscles attached to the arytenoid 
and thyroid cartilages, the tenseness of the vocal cords 
is regulated, and the various pitches of voice produced. 



iyo ELEMENTS OF MAMMALIAN ANATOMY. 

The trachea, or windpipe, is the tube leading from the 
larynx to the lungs (Fig. 54). Its walls are prevented 
from collapsing by the presence of about forty-five carti- 
laginous rings which are incomplete dorsally. Before 
passing into the lungs the trachea bifurcates into a right 
and a left bronchus. The trachea and bronchi are lined by 
ciliated columnar epithelium. The cilia project freely 




*nustU£* 

Fig. 80. — Diagrammatic Transverse Section of the Chest. 
ao, Aorta ; br, bronchus ; crd, spinal cord ; esoph, esophagus ; hd, head of 
rib ; pa, parietal pleura ; pc, cavity of the pleura ; sp, spinous process ; 
st, sternum ; tb, tubercle of rib ; tr, transverse process ; vp, visceral 
pleura ; t, thoracic duct ; n, sympathetic nerve cord ; az, azygos vein ; 
trc, trachea; v, pulmonary veins. 

into the lumen from the columnar walls, and are always 
waving in such a manner as to carry the secreted mucus 
lodged thereon toward the mouth, thereby preventing 
the lungs from becoming clogged with foreign material. 
Ciliated cells with the cilia in action may be easily demon- 
strated by scraping very lightly a little mucus from the 
posterior part of the roof of the frog's mouth, and mount- 



THE RESPIRATORY SYSTEM. 



171 




Fig. 81. — Photograph of a Lung Corrosion of a Puma in Morpho- 
logic Museum op Princeton University. The specimen was 
prepared by Mr. Sylvester. The trachea with all its ramifications 
was injected with white paraffin, and the pulmonary artery with red 
paraffin, after which the lung substance was eaten away with acid. 

tr, Trachea; br, bronchus; b, bronchia; c, bronchiole. The pulmonary 
artery and its branches are much darker than the air tubes. 



172 



ELEMENTS OF MAMMALIAN ANATOMY. 



ing the same in a drop of saliva on a glass slip, which 
is then to be examined with a microscope magnifying 
about 300 diameters. The diaphragm of the microscope 
should be arranged so as to admit but little light. 

The lungs together with the heart fill up the greater 
part of the thoracic cavity. In a cat recently killed the 
lungs may be expanded by tying a piece of glass tubing 
on the trachea and blowing into it strongly for a few 
seconds. Each lung is completely invested by a sac of 

delicate transparent serous mem- 
brane called pleura (Fig. 80). 
Each sac is reflected at the root 
of the lung, where the blood- 
vessels and bronchus enter, so as 
to form a parietal layer lining its 
half of the thoracic cavity. The 
median space between the two 
sacs is called the mediastinum. 
The anterior or ventral medias- 
tinum contains the heart. The 
dorsal or posterior mediastinum 
contains the esophagus and 
aorta. 
Each lung is divided by deep clefts into several lobes. 
The left lung is composed of two large lobes and a small 
one. The right lung consists of four unequal lobes. The 
cephalic end of the lung is the apex and the caudal end, 
resting against the diaphragm, is the base. The bronchi, 
as they are continued into the lungs, subdivide into 
smaller tubes, whose later subdivisions are the bron- 
chioles. The latter, dividing like the branches of a tree, 
finally terminate in blind pouches known as injundibula 
or alveoli, the walls of which are thickly beset with 
microscopic sac-like evaginations named air sacs (Figs. 




Fig. 82. — The Termination 
of the Bronchiole c in 
Fig. 81. 

br, Bronchiole; at, alveolus 
showing about a dozen air 
sacs or air cells. — {From 
Martin's " Human Body.") 



THE RESPIRATORY SYSTEM. 1 73 

81 and 82). The walls of these air sacs are very thin, 
somewhat like the peritoneum. Over them course numer- 
ous thin- walled capillaries, so that the carbon dioxid of 
the blood passes out into the air as the oxygen passes 
into the blood. Expiration is the process of forcing the 
air out of the lungs which have been filled by an inspira- 
tion chiefly effected by depressing the diaphragm and 
elevating the ribs. The two processes together are 
spoken of as a respiration. 



PRACTICAL QUESTIONS AND SUGGESTIONS. 

1. Of what four elements are the soft parts of the body largely com- 
posed? 

2. What waste gas is formed in every part of the body exercised? 

3. Through what three channels do waste materials pass from the 
blood? 

4. Describe the manner in which the oxygen of the air reaches the 
blood. 

5. Write a description of the pharynx. 

6. Bisect the larynx in the sagittal plane, make a drawing of the cut 
aspect, and label all features. 

7. How many cartilaginous rings in the trachea and what is their 
use? 

8. Describe as much of the pleura as can be seen in your specimen. 

9. Do the right and left bronchi have the same number of main 
branches? 

10. Why do the air cells seldom become clogged? 

1 1 . What muscles are largely used in respiration ? 

12. Describe the hyoid bone as seen from your dissection. 

13. What part of this bone can you feel beneath your mandible? 

14. How does the carbon dioxid given off by the cells in the foot reach 
the lungs? 

15. What causes the air to enter the lungs? 

16. Innate the lungs of a freshly killed animal by forcing air from 
your lungs into a glass tube tied into its trachea. 

17. After retaining a full inspiration of air as long as possible, expire 
it through a glass tube into the bottom of a two-liter bottle and insert 
into the bottle a lighted splinter. 

18. Describe the pulmonary circulation. 



THE EXCRETORY AND REPRODUCTIVE 
SYSTEMS. 

As explained in the last section, a portion of the waste 
products produced by the activity of the cells of the 
body is passed off through the lungs, but some other 
outlet must be provided for the excretions that are not 
in the form of gases. These liquid excretions, containing 
various salts and urea, pass off through the kidneys and 
the glands of the skin. 

The latter are of two kinds, sudoriparous or sweat 
glands, and sebaceous or oil glands, with ducts opening into 
the hair follicles near the surface. The sweat glands lie 
deeper than the sebaceous glands. The former are sub- 
cutaneous and consist of a more or less coiled tube with 
a straight duct opening on the surface. They are most 
abundant on the tip, of the nose and the balls of the 
feet. The sebaceous glands are very numerous all over 
the body. Both are of microscopic size. 

A still more important part of the excretory system is 
the urinary system, consisting of the kidneys, two ureters 
leading from the kidneys to the bladder, the bladder, and 
the urethra. 

The student should note that the kidney is not en- 
veloped by the peritoneum, like the other abdominal 
organs, but lies dorsad to it and is encased by a fibrous 
covering known as the capsule. The hilus is that portion 
of the concave surface where the renal artery and vein 
and ureter enter. A median longitudinal section of the 
kidney will show that the ureter within the kidney 

174 



THE EXCRETORY AND REPRODUCTIVE SYSTEMS. 



175 



enlarges, forming the pelvis, into which projects the renal 
papilla (Fig. 84). This is better demonstrated in a 
transverse section. 

The substance of the kid- 
ney is composed of an outer 
cortical layer, about a half 
centimeter thick, and an 
inner medullary substance 
adjacent to the pelvis, and 
projecting into the latter in 
the form of a papilla. In 
the cortical substance are 
hundreds of Malpighian 
bodies, each composed of a 
ball of capillaries (Fig. 84) 
enveloped by the invagin- 
ated enlarged extremity of 
a tubule which carries away 
the urine by a tortuous 
course to the papilla (Fig. 
85). In the Malpighian 
bodies the water and other 
mineral substances of the 
urine are extracted from the 
blood by means of the epi- 
thelial cells forming the 
inner wall of the capsule of 
Bowman. These urinary 
products pass through the 
proximal convoluted tubule 
and the loop of Henle to the 

distal convoluted tubule, where they are mingled with the 
urea extracted from the blood by the columnar epithelial 
cells of the tubule. From this point the excretions flow 




Fig. 83. — Ventral Aspect of Fe- 
male Urino-genital System 
with the Bladder Pulled to 
One Side. 

a, Entrance of the urethra into the 
vestibule; ao, aorta; bl, bladder; 
el, clitoris; en, cornu or horn of 
the uterus ; ft, Fallopian tube, the 
left one is cut off ; fm, fimbriated 
extremity of the Fallopian tube ; 
kd, kidney; I, ovarian ligament; 
ov, ovary; ra, renal artery; rv, 
renal vein ; re, rectum ; ur, ureter ; 
ut, body of the uterus ; uth, ure- 
thra; vc, vena cava; vg, vagina; 
vs, vestibule. 



176 



ELEMENTS OF MAMMALIAN ANATOMY. 



into the collecting tube which empties into the pelvis at 
the papilla. In a prepared micro- 
scopic section of the kidney, 
these Malpighian bodies and 
uriniferous tubules may be seen 
with a microscope magnifying 
about 200 diameters. 

The ureter is a small tube lead- 
ing from the pelvis of each kid- 
ney along the dorsal aspect of the 





Fig. 84. — Median Longitudinal Section 
oe a Kidney. 

cor, Cortical substance ; hi, hilus ; med, me- 
dullary portion; p, papilla; pi, pelvis; 
u, pyramids; ur, ureter. 



abdominal cavity to the dorsal 
and caudal end of the bladder. 
The bladder, or urocyst, is the 
sac for retaining the urine. It 
lies ventrad to the rectum, a little 
to the right of the median line, 
being held in place by the liga- 
mentum suspensorium, a fold of 
the peritoneum attached to the 
mid-ventral line. It is also at- 
tached by lateral ligaments. On 



Fig. 85. — Diagram oe the 
Structure of the Kid- 
ney between the Lines 
a and c in Fig. 84. 

ar, Arteries leading to the 
Malpighian capsules, only 
one capsule being shown; 
b, veins leading from the 
capillary network about a 
convoluted tubule as at 
n; ex, line marking the 
boundary between the cor- 
tical and medullary por- 
tions of the kidney ; cp, cap- 
sule of Bowman enveloping 
the bunch of capillaries ; d, 
distal convoluted tubule; 
hi, Henle's loop ; n, capil- 
lary network about the 
tubule; t, the bunch of 
capillaries or Malpighian 
tuft; ur, portions of urin- 
iferous tubules emptying 
into the collecting tubule 
c; xc, proximal convoluted 
tubule. 



its dorsocaudal aspect, 



THE EXCRETORY AND REPRODUCTIVE SYSTEMS. 1 77 

near where the ureters empty, the urethra originates and 
passes along the ventral surface of the vagina to the vesti- 
bule, within which it opens (Fig. 83 ) . In the male it passes 
directly from the bladder along the ventral surface of the 
rectum to the root of the penis at the pubic symphysis, 
and thence on through the corpus spongiosum to the point 
of the penis. The ureter, bladder, and urethra consist 
largely of muscular tissue, the lining being formed by 
mucous membrane. 



THE FEMALE REPRODUCTIVE SYSTEM. 

The female reproductive organs are the two ovaries, a 
pair of Fallopian tubes, a uterus, and a vagina. To 
demonstrate these, the entire ventral abdominal wall 
must be removed and the pubic symphysis severed with 
the bone-cutters. The ovaries are the small yellowish 
oval bodies about one centimeter long lying just caudad 
of the kidneys, against the dorsal abdominal wall. From 
the vicinity of each extends a tube caudad to join its 
fellow in the median line ventrad to the rectum (Figs. 54 
and 83). The cephalic portions of these are the Fallopian 
tubes, and the larger caudal portions are the cornua of 
the uterus. The junction of the cornua in the median 
line forms the body of the uterus. 

The Fallopian tube is smaller in diameter than the 
cornu of the uterus, generally more or less contorted, and 
terminates by a fimbriated expansion or mouth opening 
freely into the abdominal cavity. 

The Fallopian tubes and uterus are suspended by the 
broad ligament, or ligamentum latum, which is a fold of 
the peritoneum attached to the dorsal abdominal wall. 
The round ligament, or ligamentum rotundum, also aids 
in keeping the uterus in place. This appears as a thicken- 
15 



170 ELEMENTS OF MAMMALIAN ANATOMY. 

ing of the broad ligament when the latter is looked 
through toward the light. The round ligament extends 
from about the middle of the horn or cornu of the uterus 
ventrad of Poupart's ligament, and through the muscles 
of the abdominal wall beneath the skin of the inguinal 
region, where it gradually loses itself. It is exceedingly 
delicate and thread-like. 

The vagina extends from the uterus to the vestibule, 
opening on the surface ventrad to the anus. The small 
papilla just caudad of the orifice of the urethra on the 
ventral surface of the vestibule is the clitoris, the homo- 
logue of a part of the penis in the male. The prominent 
circular fold of mucous membrane cephalad of the orifice 
of the urethra represents the hymen, which marks the 
separation between the vagina and vestibule. This struc- 
ture may be shown by making a median longitudinal 
section through the vagina. Bartholin's glands lie on the 
lateral aspect of the vestibule, into which their ducts 
open. Each one is about the size of a small pea. The 
vagina, uterus, and Fallopian tubes are lined with mucous 
membrane in which are many glands. The mucous lining 
is surrounded by a muscular coat especially thick in the 
uterus. 

The ovaries are the organs producing the female germ 
cells or ova which when fertilized are known as the eggs 
(Figs. 54 and 83). One lies caudad of the kidney on each 
side and is invested by peritoneum, which should be care- 
fully dissected away. A microscopically prepared section 
of the adult ovary magnified about 100 diameters will 
reveal a number of ova in a more or less mature state. 
Usually a peripheral ring of very young ova is present, 
more mature ones are near the center, while one or two 
quite ripe ova are very near the circumference. As the 
ova develop, a follicle or sac known as the Graafian 



THE EXCRETORY AND REPRODUCTIVE SYSTEMS. 1 79 

follicle is formed about them. This is lined with several 
layers of epithelial cells forming the membrana granulosa. 
At one side of the follicle the membrana granulosa 
thickens and envelops the ovum, forming the discus 
proligerus. The cavity of the follicle is filled with liquor 
folliculi. When the ovum becomes almost mature, the 
walls of the follicle have grown peripherad, so as to cause 
a pin-head protuberance on the surface of the ovary 
clearly visible to the naked eye. In a fresh specimen this 
protuberance may be picked open and the ovum expelled 



Fig. 86. — Section of Ovary. X 40. 
sr, Surface of the ovary ; gr, Graafian follicle with mature ovum ; 0, ovum ; 
c, cavity of the follicle ; un, undeveloped ova ; strm, stroma or con- 
nective elements of the ovary; m, membrana granulosa; d, discus 
proligerus. 

on a slide for examination with the microscope. The 
ovum is scarcely visible to the unaided eye. The human 
ovum is still smaller. 

The ova of all mammals, except the Ornithodelphia 
(Monotremata), are very small. When the ovum becomes 
mature, the protruding wall of the follicle bursts, per- 
mitting its contents to be received by the expanded end 
of the Fallopian tube, whence it passes to the uterus. 
If the male element, the spermatozoon, enters the ovum, 
the latter is soon enveloped by a growth of mucous mem- 
brane and retained in the uterus for development. Ripe 



I S : ELEMENTS OE MA1QL\H\X ANATOMY. 

ova occur near the close of the first year of the cats life 
and new ones probably continue to mature during the 
next ten years. The discharge of the ova from the ovary 
is accompanied b3 r a constitutional disturbance, during 
which an extra amount of blood is sent to the sexual 
organs, and the sexual appetite becomes very marked. 
In the human species this disturbance occurs about every 
twenty-eight days. Mature ova occur in the human ovary 
between the thirteenth and forty-eighth years. 

Hie mammary glands of the adult female cat reach 
their full development when it gives birth to young. 
They may be seen by carefully removing the skin from 
the ventral aspect of the bod}', when they will appear 
somewhat like a thin layer of adipose tissue extending 
from near the axilla to the pubic symphysis. There are 
four teats or nipples on each side. In some mammals the 
nipples are l^ss numerous and confined either to the 
thoracic or inguinal region. In the elephant, Chiroptera, 
and Primates there are but two nipples, and they are 
thoracic. In most Ungulates the nipples are inguinal. 



THE MALE REPRODUCTIVE SYSTEM. 

The organs of generation in the male consist of the 
testes, the ducts leading from the testes to the urethra, 
the prostate gland, Cowper's gland, and the penis. 

The testes are two in number, contained in a pouch of 
integument called the scrotum, which hangs beneath the 
anus. Internally the scrotum is divided into two cham- 
bers. By dissecting away the adipose tissue covering 
the spermatic cord in the inguinal region (Fig. 51) it 
may be seen that the cord and the testes are enveloped 
by a tough sheath. This is composed of cremasU 
ia derived from the aponeurosis of the external ob- 



THE EXCRETORY AND REPRODUCTIVE SYSTEMS. 



I»I 



lique muscle, and of the tunica vaginalis. On the testis 
between these two coats is a 
thin layer of fibers forming 
the levator scroti muscle. 
The tunica vaginalis is Com- 
posed of three layers, the 
outer of which is the fascia 
propria, derived from the 
trans versalis fascia. The 
other two are derived from 
the peritoneum. 

During fetal life the testes 
lie in the abdominal cavity, 
and when they descend into 
the scrotum about the time 
of birth, a double layer of 
peritoneum is pushed down 
before them through the in- 
guinal canal, forming a di- 
verticulum whose blind end 
lies within the scrotum, 
while the constricted por- 
tion forms a channel for 
the vas deferens, spermatic 
nerve, and vessels. These 
three structures form the 
spermatic cord (Fig. 51). 
The fascia propria (tunica 
vaginalis communis) is in- 
separably united with the 
adjacent parietal layer of 
the peritoneum. The vis- 
ceral layer of peritoneum is 
quite delicate and trans- 




Fig. 87. — Ventral Aspect of the 
Male Reproductive Organs. 

cr, One of the crura of the penis; 
ep, epididymis revealed by cut- 
ting and reflecting vg, sl piece of 
the tunica vaginalis and albu- 
ginea; et, external abdominal 
ring ; it, internal abdominal ring ; 
in, inguinal canal ; g, glans penis ; 
gd, Cowper's glands ; pe, penis ; 
pr, prostate gland ; re, rectum ; 
t, testis ' from which the tQugh 
sheath composed of the levator 
scroti muscle and cremaster fascia 
has been removed, leaving it en- 
veloped by the tunica vaginalis ; 
ts, testicle from which a portion 
of the tunica vaginalis has been 
reflected; uth, urethra; ur, ure- 
ters ; vd, spermatic cord ; vdd, vas 
deferens within the abdominal 
cavity; vg, tunica vaginalis re- 
flected; vg 2 , tunica vaginalis; v, 
* spermatic vein. 



1 82 ELEMENTS OF MAMMALIAN ANATOMY. 

parent and lies close to the testis. Immediately sur- 
rounding the latter is a dense capsule, the tunica albu- 
ginea, sending septa into the interior. Within the tunica 
vaginalis is the tunica albuginea, closely investing the 
testicle, and adjacent to the epididymis penetrating the 
substance of the gland, forming a septum known as the 
mediastinum testis or corpus Highmorianum (Fig. 87). 

The testis is about 1 J centimeters long by 1 centimeter 
thick. On its dorsal surface lies the epididymis, an 
elongated body composed of an enlarged extremity, the 
globus major, and an attenuated portion, the globus minor. 
The main portion of a testicle is 
composed of many minute coiled 
tubules, tubuli seminiferi, which 
unite into a few tubules near the 
surface of the testis beneath the 
globus major, into which they ex- 
tend. These tubules are the vasa 
efferentia. The epididymis is com- 
Fig. 88. — Spermatozoa posed of a single greatly convoluted 

°x R 500 AL]S G * RM C ^ LS ' tubule of which the va s deferens is 
h, Head; t, tail. a continuation. The latter pro- 

ceeds cephalad to the external ab- 
dominal ring, which it enters to traverse the inguinal canal 
into the abdominal cavity. It then curves caudad and 
enters the urethra on its dorsal aspect in the region of the 
prostate gland. 

The inguinal canal begins with the external abdominal 
ring, which is an opening in the tendon of the external 
oblique muscle, and ends with the internal abdominal 
ring, which is an opening in the fascia of the transver- 
salis muscle (Fig. 51). By accident, a fold of the small 
intestine sometimes descends through the inguinal canal, 
which condition is known as hernia or rupture. 




THE EXCRETORY AND REPRODUCTIVE SYSTEMS. 1 83 

The penis is a cylindrical pointed body about three 
centimeters long when in repose. It is composed of two 
kinds of tissues arranged in three bundles. The corpus 
spongiosum is the median ventral bundle, extending 
throughout the length of the organ, and at the end 
forms the glans or head. The two dorsal lateral bundles 
are the corpora cavernosa. They form the greater part 
of the penis proximad of the glans, and by diverging 
somewhat before their attachment on either side to the 
pubis and ischium form the crura. The penis is sus- 
pended from the wall of the abdomen by a fold of in- 
tegument inserted at the base of the glans, and forming 
the prepuce. The latter is a free projection of skin 
covering the glans. In the midst of the penis is a small 
bone. The penis is the organ of copulation, and is com- 
posed of a spongy mass of elastic and muscular fibers 
richly supplied with highly distensible blood-vessels 
which when filled render the organ erect. 

The prostate gland surrounds the urethra dorsally and 
laterally about two or three centimeters from the bladder. 
This gland secretes a milky fluid which is poured into 
the urethra through many ducts, during copulation, and 
serves as a medium for the spermatozoa (Fig. 87). 

Cowper's glands are two in number, about the size of 
a pea, and lie in the angles formed by the urethra and 
the crura of the corpora cavernosa. These glands secrete 
a viscid fluid of unknown function. One duct from each 
gland opens into the urethra. 



184 ELEMENTS OF MAMMALIAN ANATOMY. 



REMARKS ON THE MAMMALIAN UROGENITAL 
SYSTEM. 

The urogenital system is subject to some variations in 
the different orders of Mammalia. In the Omithodelphia, 
the mammary glands are devoid of teats and the oviducts 
corresponding to the Fallopian tubes and horns of the 
uterus do not unite in the median line to form the body 
of the uterus, but unite with the urethra, forming the 
urogenital canal. The latter opens into an enlarged 
terminal portion of the rectum, called the cloaca. The 
ureters also open directly into the cloaca, so that there 
is but one external opening for the genital and excretory 
products. In the above features the Monotr ernes resem- 
ble the Amphibia and reptiles. All mammals are vivip- 
arous except the Monotr emata, which are oviparous, 
laying eggs as large as those of the robin. The Orni- 
thorhynchus incubates its eggs in an underground nest, 
while the Echidna carries hers in a temporary abdominal 
pouch. 

The Marsupialia bring forth their young in a very 
immature condition. They are then carried for several 
months in an abdominal integumentary pouch, the 
marsupium, within which are the nipples. In the Mono- 
tremata, Cetacea, Sirenia, and elephant the testes do not 
descend into a scrotum, but are retained in the primitive 
location within the abdomen. In Primates and some 
Edentates, the uterus is merely a pear-shaped body 
without any cornua, the Fallopian tubes leading directly 
into the body of the uterus. 

In the ox, bears, seals, and cetaceans the kidneys are 
distinctly tabulated. Internal evidence of lobulation is 
presented in most mammals by the renal papillae. In the 
embryo the kidneys of all mammals are lobulated. 



THE EXCRETORY AND REPRODUCTIVE SYSTEMS. 1 85 

PRACTICAL QUESTIONS AND SUGGESTIONS. 

1. What other waste products besides C0 2 result from the chemical 
action in the tissues of the body? 

2. Write a description of all parts of the urinary system visible in 
your dissection. 

3. Bisect a kidney longitudinally in the horizontal plane, draw the 
cut surface, and label all features. 

4. Explain the parts of a uriniferous tubule. 

5. Wherein does the male urinary system differ from the female? 

6. Make a drawing of the Fallopian tubes and uterus and label all 
parts. 

7. Describe location, size, external appearance, etc., of the ovary 
as seen in your specimen. 

8. How are the female reproductive organs held in place? 

9. Can you distinguish externally the termination of the uterus and 
the beginning of the vagina? 

10. Are there any eggs protruding from the ovary or any cavities 
from which eggs have been recently discharged? 

11. Describe a Graafian follicle. 

12. What must be added to the ovum to produce another animal? 

13. Name the parts of the male reproductive system present in your 
specimen and locate them. 

14. Describe the course of the spermatozoon from the testis to the 
exterior. 

15. Do all mammals nourish their young in the same manner? 

16. What mammals incubate their eggs externally? 



16 



THE NERVOUS SYSTEM. 

The nervous elements of the cat form three systems, 
known as the central, peripheral, and sympathetic. The 
central nervous system includes the brain and spinal cord. 
The peripheral system includes the twelve pairs of nerves 
emanating from the brain and the forty pairs of nerves 
emanating from the spinal cord to supply the extremities 
and trunk. The sympathetic system is composed of two 
ganglionated nerve cords extending throughout the 
trunk within the body cavity, one on either side of the 
vertebral column, and their various branches to all the 
viscera, blood-vessels, etc., of the body (Figs. 91 and 92). 



THE BRAIN. 

The central nervous system is known as the cerebro- 
spinal axis. It is composed of the brain and spinal cord. 
The brain lies within the cranial cavity and is protected 
by three membranes called the meninges. These may be 
demonstrated by cutting away the roof of the skull with 
the bone forceps. The dura mater is the tough fibrous 
membrane lining the interior of the skull. It dips down 
between the two halves of the cerebrum, forming the 
falx cerebri. Between the cerebrum and cerebellum in 
the cat it is ossified, thus forming the bony shelf or ten- 
torium cerebelli (Fig. 18). The dura mater adheres 
closely to the inner surface of the cranial cavity, forming 
the internal periosteum. The second membrane of the 
brain is the arachnoid, Between the dura mater and the 

186 



THE NERVOUS SYSTEM. 1 87 

arachnoid is the subdural space, containing a fluid having 
the nature of lymph. The arachnoid is a very delicate 
membrane which does not dip down into the sulci between 
the convolutions of the brain, as is the case with the 
pia mater, but passes across these depressions, where it 
may be easily demonstrated (Fig. ioo). 

The subarachnoidal space lies between the arachnoid 
and pia mater. The pia mater is the delicate vascular 
membrane following so closely the convolutions and sulci 
of the brain that it becomes apparent only when lifted 
carefully by the forceps. 

In order to study the brain satisfactorily each student 
should have a specimen hardened according to directions 
in the section on technique, and also should be permitted 
to examine a series of sections cut transversely about a 
centimeter thick. These sections may be mounted for 
permanent use in pasteur dishes, according to the method 
described in the "Journal of Applied Microscopy," Octo- 
ber, 1902. The brain of a calf or sheep serves the learner's 
purpose better than that of a cat, as the parts are larger, 
and they are also easier to procure. An additional ad- 
vantage is also found in the fact that there is some 
difference between the brains of the cat and calf, and 
the student must therefore rely more on his own observa- 
tions. 

External Features. — The brain is composed of five 
parts : the medulla oblongata, or myelencephalon; the pons 
Varolii and cerebellum, forming the metencephalon; the 
corpora quadrigemina and crura cerebri, composing the 
mesencephalon; the diencephalon, including the optic 
thalami and other parts bounding the third ventricle; 
and the telencephalon, or cerebral hemispheres. The 
medulla oblongata, sometimes called the bulb or stem 
of the brain, is the expansion of the spinal cord as it 



Ib6 ELEMENTS OF MAMMALIAN AXATOMY. 

passes through the foramen magnum. The pons Varolii 
is the bridge of transverse fibers seen on the ventral 
aspect of the brain just cephalad of the medulla (Fig. 94). 
The cerebellum or little brain lies on the dorsal side of 
the medulla and is partly covered by the caudal part of 
the cerebrum. The mesencephalon is not visible exter- 
nally on the dorsal aspect, but may be seen immediately 
cephalad of the cerebellum by cutting away the cerebrum 
(Fig. 98). The diencephalon is visible externally only 
on the ventral aspect of the uncut brain, where it forms 
the floor of the third ventricle. . It may be viewed as a 
whole if the dorsal half of the cerebrum including the 
corpus callosum is cut away. The telencephalon is com- 
posed of the two large hemispheres partially surrounding 
the diencephalon and mesencephalon. 

The brain is composed of two kinds of matter, white 
and gray. The former is constructed for the most part 
of fibers, while the latter is formed largely of cells. The 
outer or cortical portion of the cerebrum and cerebellum- 
is a layer of gray matter less than a half centimeter 
thick, and is disposed in folds called gyri or convolutions 
with intervening depressions termed sulci, the more im- 
portant of which are called fissures. 

The four different portions of the cerebrum are known 
as frontal, parietal, occipital, and temporal lobes, which 
occupy the respective regions of the cranial cavity. The 
frontal and parietal lobes are separated by the crucial 
fissure, extending transversely between them. The ol- 
factory lobe (usually torn off in removing the brain 
from the skull) projects from the cephalic portion of the 
frontal lobe. The parietal lobe is marked by three gyri, 
named according to location gyrus marginalis, gyrus 
suprasylvius, and gyrus ectosylvius (Figs. 89 and 90). 
The caudal portions of the gyri marginalis and supra- 



THE NERVOUS SYSTEM. 



Jf% 



sylvius constitute a portion of the occipital lobe. These 
two gyri are separated by the lateral sulcus. The supra- 
sylvian sulcus extends between the gyrus suprasylvius 
and the gyrus ectosylvius. The splenial sulcus (Fig. 92) 
separates the gyrus marginalis 
from the gyrus fornicatus on 
the mesal aspect of the parie- 
tal and occipital lobes. There 
are no definite sulci or fissures 
separating the parietal, occipi- 
tal, and temporal lobes. The 
postrhinal fissure, extending 
caudad from the fissure of Syl- 
vius, divides the temporal lobe 
into two portions on the ven- 
tral aspect. 

The ventral surface (Fig. 90) 
of the brain also presents im- 
portant features which should 
be noted by the student before 
investigating the internal 
structure. The anterior pyra- 
mids, two indistinctly differ- 
entiated bundles of fibers, oc- 
cupy the mesoventral region 
of the medulla, and cephalad 
of the pons help form the crura 
cerebri. Taterad of each pyra- 
mid is the olivary projection. 
A broad band of transverse 
fibers appearing just caudad 

of the pons Varolii and laterad of the anterior pyramids 
is the corpus trapezoideum. 

The pons Varolii is itself composed of a band of 




Fig. 89. 



OF 



Dorsal Aspect 
the Brain. 
a, Gyrus marginalis; ac, white 
matter of the cord; ad, gray- 
matter of the cord; b, gyrus 
suprasylvius ; c, gyrus ectosyl- 
vius ; cr, crucial fissure ; ce, lat- 
eral lobe of cerebellum ; d, lat- 
eral sulcus; e, suprasylvian 
sulcus; Ig, great longitudinal 
fissure; md, medulla oblon- 
gata ; n, first spinal nerve ; ol, 
olfactory lobe; p, posterior 
pyramids; sp, spinal cord; v, 
vermis of cerebellum. 




Fig. 90. — Ventral Aspect of the Brain. 
3, 4, 5, 6, 7, 8, 9, 10, 11, 12, The cranial nerves; a, ophthalmic branch 
of the trigeminal nerve; an, anterior pyramids; at, anterior horn of 
gray matter; b, superior maxillary branch of the trigeminal nerve; 
11a, eleventh cranial nerve with roots from the spinal cord ; c, mandib- 
ular branch of the trigeminal nerve ; ca, corpus albicans ; cb, cere- 
bellum ; cc, canalis centralis ; en, cornea ; ct, cut surface of spinal cord ; 
ex, external rectus muscle; cr, crus cerebri; g, Gasserian ganglion 
of the trigeminal nerve ; hi, pyriform lobe ; in, opening into the tuber 
cinereum revealed by removal of the infundibulum and pituitary 
body ; i, internal rectus ; io, inferior oblique ; ir, inferior rectus ; n x and 
n 2 , first and second spinal nerves; ol, olfactory lobe; op, optic com- 
missure ; ot, optic tract ; p, posterior horn of gray matter ; pt, anterior 
perforated space ; pv, pons Varolii ; r, mesal or inner root of olfactory 
nerve ; rt, lateral root of olfactory nerve ; pr, postrhinal fissure ; sy, 
Sylvian fissure ; s, superior rectus muscle ; tz, corpus trapezoideum ; 
x, external arciform fibers. 



190 



THE NERVOUS SYSTEM. 191 

transverse fibers which on either side forms the middle 
peduncle of the cerebellum, commonly called the crus 
cerebelli ad pontem medullae. The fibers originate either 
in cells of the medulla or those of the cerebellum. 

The crura cerebri, or peduncles of the cerebrum, the 
ventral portions of which are continued as the anterior 
pyramids (Fig. 90), are seen just cephalad of the pons. 
Their fibers unite the cerebrum to the rest of the brain 
and the spinal cord. In the space between the crura 
and the optic chiasm is a prominent projection, the 
terminal nodular portion of which is the pituitary body 
or hypophysis. It occupies the pituitary fossa of the 
skull and is usually torn off in removing the brain. 
Caudad of the hypophysis are two small rounded white 
bodies, the corpora albicantia. The tuber cinereum, a 
slightly elevated mass of gray matter behind the optic 
chiasm, bears on its surface the funnel-shaped stalk, the 
infundibulum, to which the hypophysis is attached. If 
the two latter parts are removed, there is seen a small 
elongated aperture through the tuber cinereum into the 
third ventricle (Figs. 90 and 92). 

The optic commissure, or optic chiasm, is the commissure 
formed by the crossing of the optic nerves just cephalad 
of the tuber cinereum. The prolongation of the optic 
nerves dorsad from the optic commissure forms the 
optic tracts, partly covered by the temporal lobes. On 
either side of the median fissure just cephalad of the 
optic chiasm is a somewhat triangular area known as 
the anterior perforated space because of the numerous 
vessels that enter the brain in this region. Laterally this 
space is bounded by the lateral olfactory tract or lateral 
root of the olfactory nerve, which presents the appearance 
of a band of white fibers extending from the olfactory 
lobe into the temporal lobe. The mesal or inner root of 



192 



ELEMENTS OF MAMMALIAN ANATOMY. 




the olfactory nerve is seen adjacent to the median ventral 
line cephalad of the anterior perforated space. The 
olfactory lobes project from the cephalic ventral portion 
of the cerebrum and give origin to the first pair of cranial 
nerves. 

Internal Structure. — The canalis centralis, a small canal 
extending throughout the center of the spinal cord, 
enlarges in the region of the brain, 
forming four cavities or ventricles 
communicating with each other by 
narrow channels. The brain is there- 
fore to be considered as a hollow 
structure. The first and second ven- 
tricles, also known as lateral ventricles, 
occupy the cerebral hemispheres (Fig. 
91). The third and fourth ventricles 
lie in the median line, and are there- 
fore well seen in a sagittal section of 
the brain (Fig. 92). 

The Ventricles of the Brain. — The 
fourth ventricle is visible on the dorsal 
aspect of the medulla oblongata (Fig. 
92). It is about three centimeters 
long by one centimeter wide, and lies 
ventral to the cerebellum. This ven- 
tricle is merely an expansion of the 
canalis centralis of the spinal cord. Its roof is very thin 
and consists of two portions, one of which, the superior 
medullary velum, sometimes called the valve of Vieussens, 
covers the cephalic half of the ventricle ; the other portion 
is the inferior medullary velum, lying over the caudal 
half. The latter velum is composed of a fold of pia 
mater tucked in between the cerebellum and medulla, 
in addition to a layer of epithelial cells on the ventricular 



Fig. 91. — Diagram of 
Ventricles of the 
Brain Viewed 
Dorsaeey. 

ah, Anterior horn of 
the right lateral ven- 
tricle; as, aqueduct 
of Sylvius; cc, can- 
alis centralis of the 
spinal cord; 3 and 
4, third and fourth 
ventricles; ra, fora- 
men of Monro; mi, 
middle horn or cor- 
nu of the ventricle. 



THE NERVOUS SYSTEM. 1 93 

aspect of the pia mater. Some nervous matter in addi- 
tion to the pia mater and epithelium forms the superior 
velum. Two longitudinal vascular fringes, hanging from 
the roof of the ventricle on either side of the mid-line, 
form the choroid plexus, which is merely a network of 
blood-vessels carried by a reflected portion of the pia 
mater. 

Cephalad the fourth ventricle is continued as a small 
canal, the iter, or aqueduct of Sylvius, which lies ventrad 
to the corpora quadrigemina and opens into the third 
ventricle (Fig. 92). The latter is a narrow, vertical, 
cleft-like space between the optic thalami. The two 
thalami are united by the soft or middle commissure, 
better designated as the mass a intermedia, extending 
through the ventricle. Unless this ventricle has been 
injected with a starch mass through the infundibulum 
before the brain was hardened, its cavity will not exceed 
a millimeter in width. The roof is formed much in the 
same manner as that of the fourth ventricle, by a re- 
flection of the pia mater lined with epithelium (Figs. 92 
and 94). A sagittal section of the brain placed in a pan 
of water will show the fold of pia mater called velum 
inter positum extending cephalad from the pineal gland. 
Two folds of the pia mater hanging on either side from 
near the median line form the choroid plexus as in the 
fourth ventricle. The body of the fornix lies dorsad of 
the membranous roof of the ventricle. In the floor lie 
the corpora albicantia, the infundibulum, the tuber 
cinereum, and the optic commissure. Cephalad the 
third ventricle communicates with the lateral ventricles 
by slit-like apertures, the foramina of Monro, passing 
laterad and ventrad of the anterior pillars of the fornix. 

The lateral ventricles are found in the cerebral hemi- 
spheres ventrad to the corpus callosum. They are the 



194 



ELEMENTS OF MAMMALIAN ANATOMY. 



largest ventricles of the brain. In order to view them 
satisfactorily, the entire dorsal portion of the brain down 
to the corpus callosum must be cut away, and a hole 
cut through the corpus callosum. A number of cross- 
sections of the cerebral hemispheres should also be 
studied. 



M^ 



F> 



.tn^ 




Fig. 92.— Sagittal Section of the Brain. 
ac, Anterior commissure; av, arbor vitae; c, habena; cc, canalis centralis; 
cb, cerebellum; cm, middle commissure or massa intermedia; cr, 
sulcus crucialis; cpq, corpus quadrigemina ; ex, choroid plexus of 
third ventricle — the dark line dorsad of ex is the velum interpositum ; 
/, sulcus splenialis ; fr, frontal lobe of cerebrum ; fn, anterior pillars 
of the fornix; in, inf undibulum ; it, iter, or aqueduct of Sylvius; k, 
genu of corpus callosum ; Imx, lamina terminalis ; m, splenium ; mr, 
sulcus marginalis ; med, medulla ; op, optic chiasm ; oc, occipital lobe ; 
ol, olfactory lobe; pn, pineal gland; po, pons Varolii; pc, posterior 
commissure; pv, inferior medullary velum; pvv, superior medullary 
velum or valve of Vieussens ; 3 and 4, third and fourth ventricles. 



Each ventricle is composed of a body from which pro- 
jects an anterior cornu and a middle or descending cornu. 
The former extends into the frontal lobe and thence into 
the olfactory lobe, and the latter descends into the 
temporal lobe. The roof of the body of the lateral ven- 
tricle is formed by the corpus callosum (Figs. 92, 93, 
and 94) and the mesal wall by the septum lucidum, a 



THE NERVOUS SYSTEM. 195 

mass of gray matter lying between the fornix and the 
corpus callosum. A fringe of pia mater projects through 
the foramen of Monro into the lateral ventricle, where it 
forms the choroid plexus. The lateral ventricles are lined 
with the epithelial layer common to the other ventricles. 

These cavities within the central nervous system result 
from the manner in which the brain and cord are formed. 
In the embryonic life of most vertebrates the nervous 
system appears as a trough of matter extending dorsally 
throughout the length of the body. The sides of this 
trough grow dorso-mesad, thus forming a roof and 
thereby converting the trough into a canal which in the 
spinal cord becomes the canalis centralis, and in the 
brain the ventricles. This continuous cavity of the 
central nervous system contains a fluid having the nature 
of lymph. 

The Commissures of the Brain. — The paired portions of 
the brain are united across the median line by bands of 
fibers known as commissures, two of which are visible 
on the ventral surface of the brain, and the others may 
be seen in a sagittal section (Fig. 92). 

The pons Varolii is the commissure on the ventral 
aspect of the medulla. Its fibers pass into the cerebellum 
on either side, forming the middle peduncle or crus cerebelli 
ad pontem. The optic commissure or optic chiasm is 
formed by the crossing of the optic nerves, cephalad of the 
tuber cinereum. Some of the fibers originating in the cells 
of the retina of one eye pass by this commissure directly 
to the cells in the retina of the other eye, while a second 
set passes from the eye to the optic tract on the opposite 
side of the brain, and still a third set, originating in one 
corpus quadrigeminum, passes by the optic commissure 
direct to the opposite corpus quadrigeminum (Figs. 92, 
100). 



196 ELEMENTS OF MAMMALIAN ANATOMY. 

The corpus callosum is the largest commissure of the 
brain. It joins the two cerebral hemispheres, and forms 
the roof of the lateral ventricles. This broad plate of 
fibers (Figs. 92, 93, 94, 95), which may be seen at the 
bottom of the great longitudinal fissure by pressing the 
hemispheres slightly apart, is about one millimeter thick 
and three centimeters wide. Laterally the fibers radiate 
in all directions to the gray matter of the cortex. The 
ventral bend of the median cephalic portion of the 
callosum is the genu or knee. The caudal border is the 
splenium. 

The fornix lies ventral to the callosum (Figs. 92 and 
94) and consists of a median plate of fibers, the body, 
two posterior columns, and two anterior columns or pillars. 
The median plate or body of the fornix sends some fibers 
into the ventral surface of the callosum. From the 
cephalic border of the body near the median line the 
two anterior columns, or pillars, descend in a curve, 
forming the cephalic boundary of the third ventricle as 
far ventrad as the anterior commissure. Here the two 
columns diverge slightly from the median line, but con- 
tinue their descent, curving caudad to their termination 
in the corpora albicantia. The posterior columns, or 
crura, descend from the caudal border of the body, 
curving laterad into the median cornu of the lateral ven- 
tricle, and gradually unite with the cornu ammonis. 
The cornu ammonis, or hippocampus major, is a thickened 
projecting fold of the wall of the median cornu (Fig. 93). 
The free lateral margin of the posterior pillar or crus of 
the fornix is the -fimbria, or tcenia hippocampi. Adjacent 
to the median line in either hemisphere, a thick lamina of 
matter, the septum lucidum, stretches from the cephalic 
part of the fornix dorsad to the callosum. The very 
narrow cavity formed by the adherence of the margins 



THE NERVOUS SYSTEM. 



197 



of the septum of one hemisphere to those of the septum 
in the other hemisphere is sometimes called the fifth 
ventricle. Between each anterior pillar of the fornix and 




Fig. 93. — Dorsal Aspect of the Brain with the Cerebellum and 
the Dorsal Third op the Cerebrum Removed and Most of the 
Corpus Callosum Cut Away from the Right Half. 

ac, Right anterior corpus quadrigeminum ; c, commissure of the quadri- 
gemina; ca, the united superior and inferior peduncles of the cere- 
bellum ; cr, the middle peduncle or crus cerebelli ad pontem ; cs, corpus 
striatum; ct, edge of corpus callosum cut slightly to the left of the 
median line; cal, dorsal surface of the callosum into which a hole 
has been cut; hp, hippocampus major, or cornu ammonis, in the 
median cornu of the lateral ventricle; h, hippocampus major near 
where it is joined by the fibers of the crus of the fornix; i, uncut 
portion of the callosum ; md, medulla oblongata ; n, anterior columns 
or pillars of the fornix; o, gray cortex of the cerebrum; p, posterior 
crus of the fornix; pn, pineal gland, cephalad to which is the heavy 
white line, the commissure of the habenae or taeniae thalami; pp, 
funiculus gracilis; re, funiculus of Rolando; 1, funiculus cuneatus; 
ts, one of the testes or posterior corpora quadrigemina ; x, body of 
the fornix. 



the optic thalamus is a cleft, the foramen of Monro, 
leading from the third ventricle, laterad of the septum 
lucidum, into the lateral ventricle. 



198 ELEMENTS OF MAMMALIAN ANATOMY. 

The three remaining commissures are known according 
to their location as the anterior, middle, and posterior. 
The anterior commissure (Figs. 92 and 95) perforates the 
corpora striata, extending across the median line imme- 
diately cephalad of the anterior pillars of the fornix. It 
is about two millimeters in diameter. The middle com- 
missure, or massa intermedia, lies between the optic 
thalami. It is sometimes called the soft or gray com- 
missure. It is nearly one centimeter in diameter and 
passes through the third ventricle (Fig. 92). The pos- 
terior commissure is a cord of fibers about a millimeter 
in diameter connecting the caudal portions of the optic 
thalami. 

The Basal Ganglia. — A semi-independent group of nerve 
cells forming a definite mass is known as a ganglion. 
In the ventral portion of the brain lie three pairs of 
large ganglia, called corpora quadrigemina, optic thalami, 
and corpora striata. To study them, the entire dorsal 
surface of the brain down to and including the corpus 
callosum should be removed. 

The corpora quadrigemina (Fig. 93) lie cephalad of the 
medulla, and consist of an anterior pair, the nates, and 
a posterior pair, the testes. A narrow canal, the iter, 
or aqueduct of Sylvius, leads from the fourth ventricle 
through the corpora quadrigemina (Fig. 92) from the 
fourth ventricle to the third ventricle. The nates lie 
nearer to the midline than the testes, which are slightly 
separated by a depression occupied by the middle portion 
of the central lobe of the cerebellum. The testes are 
united by a white commissure. The posterior commis- 
sure of the brain unites the cephalic portions of the nates 
(Fig. 92). Its cut end may be seen ventrad to the base 
of the pineal gland. 

Laterally each pair of the corpora quadrigemina is 



THE NERVOUS SYSTEM. 



199 



prolonged into two white bands, the anterior and pos- 
terior brachia. The latter are about a half centimeter 
long, and pass forward beneath a pisiform ganglion, the 
corpus geniculatum internum or mediate. The anterior 
brachia pass from the cephalic end of the nates laterad 
beneath the caudal projections of the optic thalami, 
where they join the optic tracts. 




5 °P*iPY *?■ 

"* op 




Ctti do V 

Fig. 94. — Cross-section of the Brain in the Plane x in Fig. 92. 
The plane is just caudad of the optic chiasm. 

1 and 2, First and second or lateral ventricles; cr, corpus callosum; cm, 
anterior pillars of fornix; ex, choroid plexus of lateral ventricle; ex', 
choroid plexus of third ventricle; cxt, gray cortex; ea, ependyma or 
endyma lining the ventricles; /, median longitudinal fissure; h, 
habena, or taenia thalami; mc, middle commissure, or massa inter- 
media; n, fibers of the optic tract as they enter the external genic- 
ulate body s; 0, fornix ; r, caudal portion of nucleus lenticularis ; 
op, optic thalamus ; oc, optic tract as it leaves the chiasm ; si, septum 
lucidum; vn, part of third ventricle dorsad to the commissure; v, 
third ventricle ; t, fibers of optic tract. 



Homologues of the corpora quadrigemina exist in all 
vertebrates. In them originate largely the optic nerves, 
and therefore their size is in proportion to the animal's 
power of sight. In the mole, which has little use for 
eyes, the anterior pair is rudimentary. 

The optic thalami form the largest pair of basal ganglia, 
and lie cephalad of the corpora quadrigemina and form 



200 ELEMENTS OF MAMMALIAN ANATOMY. 

the lateral walls of the third ventricle, across which they 
meet, forming the massa intermedia, or middle com- 
missure. 

On the dorsal aspect of each thalamus, near the median 
line, is a longitudinal band of white fibers called the 
habena, or tenia thalami, which at its caudal limit is 
united to its fellow by the commissura habense. The 
thalamus is composed largely of gray matter, but there 
are two important bundles of fibers, known as the optic 
tract and internal capsule (Fig. 94), appearing on its 
lateral surface. The optic tract, of which the optic nerve 
is a continuation, arises by two roots, the larger of which 
comes from the cells forming the lateral geniculate body, 
which is the lateral and caudal projection of the thalamus. 
The internal capsule, well shown in a transverse section, 
is composed mainly of the fibers descending from the 
cells of the parietal region of the cortex. 

The pineal gland, or pineal body (Fig. 92), is a conical 
projection about a half centimeter long, from the caudal 
part of the dorsal surface of the thalamus. It is a ves- 
tigial structure which in some of the lower vertebrates 
in early geological time functioned as a third eye. In 
Hatteria, a New Zealand lizard about a foot long, the 
eye is present, projecting slightly through a foramen in 
the parietal bone. Traces of this third eye with a lens 
have also been noticed in the embryo of the viper and 
some of the lizards. 

The corpora striata are the most cephalic of the basal 
ganglia and are somewhat pear-shaped, the larger ends 
being cephalad and nearer the median line than the 
caudal portions, which curve laterad around the optic 
thalami (Fig. 93). They form a part of the floor of the 
lateral ventricles, and are pierced by the anterior com- 
missure (Fig. 95), a small cord of white fibers. 



THE NERVOUS SYSTEM. 



20I 



The corpus striatum consists of both white and gray 
matter. The latter, composed of cells, is disposed in 
two chief nuclei or masses, known as the nucleus cauda- 
tus, lying median and cephalic, and the nucleus lenticu- 
laris, which is more lateral and caudal (Fig. 95). The 
center of the nucleus lenticularis is laterad of the optic 
thalamus and dorsad of the crus cerebri. A thin layer 
of white matter, the lamina semicircular is, separates the 




vn cm 



Fig. 95. — Cross-section of the Brain through the Anterior Com- 
missure. 

an, Arachnoid; ce, external capsule; cl, corpus callosum; cm, anterior 
commissure ; fxc, f alx cerebri ; /, great longitudinal fissure ; fx, anterior 
pillars of the fornix; ic, internal capsule; n, radiating fibers of cal- 
losum ; in, septum lucidum ; nc, nucleus caudatus of corpus striatum ; 
/, nucleus lenticularis; p, pia mater; vls t superior longitudinal sinus; 
vn, third ventricle; v, lateral ventricle. 



optic thalamus from the nucleus caudatus. A few fibers 
from the crus cerebri form the lamina semicircularis, 
whose edge may be seen in the floor of the lateral ven- 
tricle on the lateral boundary of the nucleus caudatus. 
A group of fibers, known as the internal capsule, separates 
the optic thalamus from the nucleus lenticularis, laterad 
of which is the external capsule, a group of fibers probably 
descending from the cells of the cerebral cortex. The two 
nuclei of the corpus striatum are connected by fibers, 
17 



202 ELEMENTS OF MAMMALIAN ANATOMY. 

and other fibers connect these nuclei with the cortex of 
the cerebrum and the optic thalamus. 

The Medulla Oblongata. — The medulla oblongata, or 
myelencephalon, is the stem of the true brain and extends 
from the point of origin of the first spinal nerve to the 
pons Varolii. The cerebellum must be removed in order 
to study carefully the features of the medulla, and as 
it is cut away the student should notice just ventrad to 
it the very thin roof of the fourth ventricle. Its caudal 
portion, composed of a reflection of the pia mater lined 
with epithelium, takes the name of inferior medullary 
velum, and the cephalic part, formed of pia and a thin 
layer of nervous matter, is called the anterior medullary 
velum, or valve of Vieussens (Fig. 92). 

The fourth ventricle (Figs. 92 and 93) is an enlargement 
of the canalis centralis of the cord. The clavae, or expan- 
sions of the funiculi graciles, the three peduncles or crura 
of the cerebellum, and the testes or colliculi inferiores 
form its lateral boundaries. Its cavity is shallow and 
pointed at either extremity. The floor, called fossa 
rhomboidea, is formed by the continuation of the gray 
matter of the spinal cord. Where the ventricle is widest 
a tract of fibers, the stria medullaris, arises from the 
midline and proceeds laterad to help form the auditory 
nerve. 

Laterad of the clava a larger band of fibers, the 
funiculus cuneatus, runs parallel with a more lateral 
lying bundle, the funiculus cuneatus lateralis, or funiculus 
of Rolando. These three bands of fibers compose the 
restiform body, or inferior peduncle of the cerebellum. 
On the ventral aspect of the medulla may be seen the 
anterior pyramids, composed of a band of fibers lying 
on either side of the median line and apparently emerging 
from the pons. They form a section of the crossed 



THE NERVOUS SYSTEM. 203 

pyramidal or motor tract connecting the brain with the 
cord. The olivary eminence lies just laterad of the 
pyramid. The fact that seven posterior cranial nerves 
originate from the medulla shows the importance of this 
part of the brain. The destruction of the respiratory 
centers, or vital knot, lying ventrad to the caudal end 
of the fourth ventricle causes instant death. 

The Cerebellum, or Little Brain. — The cerebellum, 
which in the cat lies caudad of the cerebrum and dorsad 
of the medulla, resembles the cerebrum in being com- 
posed of an outer layer of gray matter or cells and an 
inner mass of white matter made up of fibers. While 
within the cerebrum there are several important ganglia 
or masses of gray matter, in the cerebellum only one 
chief mass of gray matter, the corpus dentatum, is present 
in each hemisphere. 

The outer layer of gray matter, known as the cortex, 
is folded into numerous convolutions, between which are 
deep sulci (Fig. 92). The central core of white matter 
forms an arborescence known as the arbor vita. 

The cerebellum (Fig. 89) is seen to consist externally 
of two lateral portions, the cerebellar hemispheres, a 
median vermiform process and three pairs of peduncles 
or bands of fibers uniting it with other parts of the 
brain and cord (Fig. 93). The separation between the 
hemispheres and vermis or vermiform process is most 
marked on the cephalic aspect. 

The peduncles are named, according to their location, 
superior, middle, and inferior. The middle peduncle, or 
crus ad pontum, is a dorsal prolongation of the fibers of 
the pons Varolii (Fig. 90). In order to display the other 
peduncles a portion of the cerebellum must be cut or 
picked away with the forceps. The superior one, known 
also as the brachium conjunctivum, extends as a cord 



204 ELEMENTS OF MAMMALIAN ANATOMY. 

of fibers along the cephalic half of the fourth ventricle 
beneath the corpus quadrigeminum. The inferior pedun- 
cle, or restiform body, forms part of the boundary of 
the caudal half of the fourth ventricle and enters the 
cerebellum between the other two peduncles. It is com- 
posed largely of fibers from the spinal cord. 

PRACTICAL QUESTIONS AND SUGGESTIONS. 

1. Describe the meninges of the central nervous system. 

2. Which of the five parts of the brain are exposed dorsally? 

3. Draw the lateral aspect of the brain and label all features. 

4. Draw the ventral aspect of the brain and label all features. 

5. Draw the dorsal aspect of the brain after the dorsal portion, in- 
cluding corpus callosum and fornix, has been removed. 

6. Describe the differences existing between the gyri and sulci of 
your specimen and the one described in the text. 

7. Write a description of the ventricles, giving dimensions and bound- 
aries. 

8. Describe the attachment of the pineal body. 

9. Which of the cranial nerves derive their name from their function? 

10. Name the foramina giving passage to one or more of the cranial 
nerves. 

11. From which of the five parts of the brain do most of the cranial 
nerves originate? 

12. Describe the choroid plexus. 

13. What is the internal capsule? 

14. Draw a cross-section of the brain made by cutting through the 
optic commissure and label all parts. 

15. Draw a cross-section of the brain made by cutting through the 
middle commissure and label all parts. 

16. Draw a cross-section of the brain made by cutting through the 
corpora quadrigemina and label all parts. 

17. Write a description of the corpus callosum. 

18. Which is the smallest commissure of the brain? 

19. Explain the difference in structure between the white and gray 
matter. 

20. Describe the cerebellum. 



THE NERVOUS SYSTEM. 205 

THE SPINAL CORD. 

The spinal cord extends from the foramen magnum 
through the vertebral canal. It is more or less cylindrical 
throughout and has a diameter of about one centimeter 
except in the lumbosacral region, where it grows gradu- 
ally smaller until it is only one or two millimeters in 
diameter. In order to study the cord, one should have 
a mounted transverse microscopic section, an entire cord 
in situ with the dorsal wall of the vertebral canal re- 
moved, so that the exit of the spinal nerves may be seen. 

The membranes which envelop the spinal cord are the 
same as those that envelop the brain. The dura mater 
is the external tough coat; the pia mater, the internal 
delicate vascular coat sending a process deep into the 
anterior fissure on the ventral side; and the arachnoid, 
the very thin membrane between the two preceding. 
The arachnoid lies close against the dura mater, but is 
separated from the pia mater by the subarachnoid space, 
which is filled with a serous fluid called the cerebrospinal 
fluid. It is apparently the same as that in the ventricles 
of the brain, and seems to be of a lymphoid nature. 
In fact, the subarachnoidean space is merely a large 
lymph space similar to the cavities of the pleura and 
peritoneum. This lymph, or cerebrospinal fluid, proba- 
bly escapes from the thin walls of the capillaries covering 
the pia mater and is taken up by lymphatic vessels which 
begin in open mouths on the walls of the space. 

The cord presents two enlargements, the cervical, 
whence issue the nerves of the forelimbs, and the lumbar, 
giving origin to the nerves of the posterior limbs. Two 
deep fissures, the anterior median and the posterior 
median, penetrate about one-third through the cord, 
incompletely dividing it into halves longitudinally. The 



206 ELEMENTS OF MAMMALIAN ANATOMY. 

pia mater is prolonged into the anterior fissure, but not 
into the posterior fissure. Slightly laterad of the anterior 
median fissure issue the anterior roots of the spinal 
nerves, and at about the same distance from the posterior 
median fissure are the posterior roots of the spinal nerves. 
These two roots unite about one centimeter from their 
origin (Fig. 90). On the posterior or sensory root is a 
small ganglion located very near the junction of the two 
roots. The common spinal nerve, formed by the union 
of the two roots, almost immediately divides into four 
branches, one of which, the dorsal, supplies the muscles 
and skin along the vertebral column; a second, the ven- 
tral branch, supplies the limbs or intercostal spaces; 
while the other two branches, rami communicantes, join 
the adjacent ganglion of the sympathetic cord (Fig. 103). 
Each of the four branches contains both motor and sen- 
sory fibers, or, in other words, fibers from both roots. 

The exit and entrance of the nerve roots divide the 
white matter of the lateral half into three columns named, 
according to their location, the anterior column, the 
lateral column, and the posterior column. The first is 
ventral to the anterior nerve roots, the last is dorsal to 
the posterior nerve roots, while the lateral column is 
between the roots. 

The elements of the spinal cord, like those of the 
brain, are of two kinds — the cells composing the gray 
matter and the fibers composing the white matter. 
While in the brain the gray matter is largely on the 
surface, forming the cortex, in the cord it occupies the 
central region. A canal, the canalis centralis, about one- 
half a millimeter in diameter, extends throughout the 
cord, opening into the fourth ventricle of the brain. A 
cross-section of the cord shows the gray matter arranged 
in the shape of a letter H . The ventral columns of gray 



THE NERVOUS SYSTEM. 



207 



matter are the anterior horns, and the posterior columns, 
the posterior horns (Fig. 96). 

Many of the fibers extend in a longitudinal direction 
throughout the cord, but the roots of the spinal nerves 
upon entering the cord run transversely a longer or 
shorter distance, and in many cases cross to the opposite 
side. It is thought that the anterior root fibers are, for 




Fig. 96. — Diagrammatic Cross-section of the Spinal Cord. The cells 
and fibers are represented too few and too large in proportion to the 
size of the cord. 

ag, Anterior horn or column of gray matter; a, nerve process of the cell 
c; an, anterior root ; cc, canalis centralis ; c, one of many cells forming 
the ganglion on the posterior root; d, posterior fissure; e, cell giving 
off an axis-cylinder process into the anterior root ; dn, dorsal branch ; 
/, cut-off fibers; gn, ganglion of posterior root; i, axis-cylinder pro- 
cess of the cell to; nc, junction of anterior and posterior roots; ps, 
posterior root of nerve ; pg, posterior horn of gray matter ; s, terminal 
arborization of part of fiber from c , v, anterior median fissure ; vn, 
ventral branch of nerve; van, axis-cylinder process of anterior horn 
cells ; x, the part of the posterior root fiber extending caudad in the 
cord. 



the most part, the axis-cylinder processes of the cells in 
the anterior horn (Fig. 98). 

Each posterior root fiber after passing into the cord 
separates into two parts one of which extends cephalad, 
the other caudad (Fig. 98). Both give off branches at 
right angles, called collaterals, which terminate in arbori- 
zations about the cells of the cord. 



208 



ELEMENTS OF MAMMALIAN ANATOMY. 



Each nerve cell presents two kinds of processes, proto= 
plasmic processes or dendrites and an axis=cylinder pro= 

cess (Fig. 97). The dendrites, except in the ganglia 
outside of the central nervous system, are usually several 
in number and comparatively short, while there is but 




Fig. 97. — Cell from the Central Nervous System. X 100. 
a, Dendrites or protoplasmic processes; ax, axis-cylinder process; n, 



nucleus of the cell body. 



one axis-cylinder process from each cell, which may 
be more than a foot in length. A number of axis-cylin- 
ders (nerve fibers), each of which is surrounded by a 
sheath, the neurilemma, constitutes a nerve bundle 
or nerve. Every axis-cylinder or nerve fiber originates 
in a cell, but terminates freely either within the central 











!"-m 

^ <*i ! f j- 1 1 

zt m-A>-f.+^ 1 t/ ^ i j 




Fig. 98. — Diagram showing the Relation op some of the Cells and 
Fibers of the Spinal Cord. Lateral aspect of the cord. 

a, Anterior median fissure ; ac, cells of the anterior horn ; an, anterior root 
of spinal nerve ; c, axis-cylinder process ; co, collateral fibers ; e, fibers 
connecting higher brain centers with cerebellum; ji, sensory fibers 
of fillet to the brain; g, gn, go, ganglion of posterior root; gr, gray 
matter ; ir, fibers of the posterior sensory tract ; /, fibers to cerebellum ; 
m, cells in the anterior horn or column of gray matter ; n, spinal nerves ; 
o, cells in the posterior horn or column of gray matter; nc, nucleus 
gracilis and nucleus cuneatus; nr, nucleus ruber; r, a fiber of pos- 
terior root ; rb, ganglion cells of medulla ; s, tract of fillet to the brain ; 
sp, fibers of superior peduncle of the cerebellum ; V , fiber of crossed 
pyramidal tract; is, point of decussation; v, division of fiber x into 
its cephalic and caudal extensions ; w, a collateral of the longitudinal 
fiber ir. 



18 



209 



2IO ELEMENTS OF MAMMALIAN ANATOMY. 

nervous system or in some other part of the body (Figs. 
97, 98). Within the central nervous system a fiber 
usually ends in an arborescence which may be contiguous 
but not continuous with the dendrites of another cell. 
The nerve processes have the power of conducting 
impulses whether derived from the cell itself or an 
external stimulus. The dendrites conduct impulses to- 
ward the cell, while the axis-cylinder conducts them 
from the cell. 

The sensory fiber r (Fig. 98) leads from the dermis 
of the cat's paw. A pin-prick in the paw causes an 
impulse to be transmitted along the fiber to the cell 
g, and thence by its axis-cylinder, x, to the point v 
within the cord where the fiber splits. From the point 
v the impulse will proceed both through the ascending 
portion of the fiber, ir, and the collateral, w. By the 
latter route it will stimulate the cell m, whose axis- 
cylinder terminates in the foreleg muscles, which are 
thereby made to contract and pull the paw away from 
the irritating object. This process may take place 
without consciousness, and is then known as reflex action. 
If, however, the impulse travels along the fiber ir, and 
thence through the fiber s to the brain, whence an im- 
pulse descends through the fiber t f , ts, the process is known 
as voluntary reaction. 



THE FIBER TRACTS OF THE CENTRAL NERVOUS 

SYSTEM. 

As before stated, the white matter of each half of the 
cord is divided by the exit and entrance of the nerve 
roots into three columns — anterior, lateral, and posterior. 
Each of these columns is subdivided into tracts which 
have special names and special functions (Fig. 99). 



THE NERVOUS SYSTEM. 



211 




In the posterior column two tracts are recognized: 
the fasciculus of Goll, occupying the mesal third of the 
column, and the fasciculus of Bur- 
dach, composing the remainder. In 
the medulla of the cat these two 
tracts may be distinguished by the 
unaided eye (Fig. 93). They are 
here called the funiculi of Goll and 
Burdach, or funiculi gracilis and 
cuneatus. Their fibers are largely, 
if not entirely, the axis-cylinder 
processes of the ganglion cells on 
the posterior roots of the spinal 
nerves. They terminate in the nu- 
clei gracilis and cuneatus, two small 
masses of nerve cells in the medulla 
laterad of the fourth ventricle (Fig. 
98) . That these fibers are processes 
of the spinal ganglion cells is proved 
by the fact that they degenerate 
if the posterior nerve roots are 
severed close to the cord. In 
whales, where the pelvic extremi- 
ties are wanting, the fasciculi of 
Goll and Burdach are very small. 

The lateral column is composed 
of five tracts : the direct cerebellar 
tract, the antero-lateral descending 
cerebellar tract, the antero-lateral 
ascending cerebellar tract or Gow- 
ers's tract, the lateral ground bun- 
dle, and the crossed pyramidal tract. 

The direct cerebellar tract occupies the superficial re- 
gion of the cord laterad of the posterior cornu of gray 



Fig. 99. — Diagram of 
Some Fiber Tracts. 
Dorsal Aspect. 

al, Antero-lateral ascend- 
ing cerebellar tract; c, 
posterior corpus quad- 
rigeminum; cer, lateral 
lobe of cerebellum, 
whose median portion 
is removed ; eg, the two 
fasciculi of Goll and 
Burdach represented as 
one; cp, crossed pyra- 
midal or chief motor 
tract ; cp' ', crossed pyra- 
midal tract in the region 
of the cerebral pedun- 
cle; dc, direct cerebellar 
tract; fi, the large part 
of the fillet derived from 
nc; nc, nuclei gracilis 
and cuneatus ; s, decus- 
sation of pyramidal 
tracts; x, sensory or 
superior pyramidal de- 
cussation; sp, superior 
peduncle of cerebel- 
lum. 



212 ELEMENTS OF MAMMALIAN ANATOMY. 

matter. Its fibers originate from the cells of the more 
central portion of the gray matter throughout the cord 
and terminate in the cerebellum. Its fibers help to 
form the inferior peduncle of the cerebellum. 

The antero-lateral descending cerebellar tract occupies 
the superficial area ventrad of the anterior horn of gray 
matter. Its fibers originate in the cells of the cerebellum 
and extend caudad in the cord. 

The antero-lateral ascending cerebellar or Gowers's 
tract occupies the superficial area laterad of the anterior 
horn. Its fibers probably originate in the cells of central 
gray matter throughout the cord, and largely terminate 
in the cerebellum. The lateral ground bundle consists 
largely of fibers with a short course, many of which are 
commissural, connecting the two halves of the spinal cord. 

The crossed pyramidal tract contains the longest 
fibers of any of the tracts of the central nervous system 
and occupies a large area just laterad of the posterior 
horn of gray matter. Its fibers originate in the cortical 
cells of the brain near the crucial sulcus (Fig. 89), and 
descend as part of the internal capsule, through the 
corpus striatum and laterad of the optic thalamus to the 
base of the brain. Here it is one of the three main tracts 
forming the crus or peduncle of the cerebrum, whence 
it extends through the pons Varolii, appearing along the 
median ventral line of the medulla as the pyramid (Fig. 
90). At the caudal end of the medulla it crosses dorsad 
to the opposite side of the cord to occupy the area laterad 
of the posterior horn of gray matter. Its fibers terminate 
largely in arborizations around motor cells of the cranial 
nerves in the brain, and the cells in the anterior horn 
of gray matter, from which originate the motor fibers 
for the muscles of the body. Therefore it is apparent 
that this tract controls largely the muscular activities 



THE NERVOUS SYSTEM. 213 

of the entire body (Figs. 98, 99, and 100). The crossing 
of the fibers of this tract in the caudal region of the 
medulla is known as the motor decussation or the de- 
cussation of the pyramidal tract. 

The limits of these various fiber tracts of the central 
nervous system cannot be determined by dissection. 
They have been worked out largely by experimental 
physiology and pathology, and by studying their embry- 
onic development when the fibers of different tracts 
are seen to acquire their sheaths (neurilemmae) at differ- 
ent periods. The portion of a nerve fiber separated from 
its cell degenerates, so that if the fibers of the crossed 
pyramidal tract were injured by accident or disease in 
the region of the medulla, all that part of the tract in 
the cord would degenerate, in consequence of which the 
subject would suffer paralysis. 

The larger portions of the tracts thus far described 
have been confined to the cord, while the remaining 
tracts to be discussed concern chiefly the brain. In 
order to understand these it is necessary to remember 
that the cortex of the brain is composed of millions of 
nerve cells which give origin to nerve fibers extending 
to other portions of the cortex, to the basal ganglia, the 
cerebellum, medulla, and spinal cord (Fig. 100). like- 
wise some of the fibers originating in the cells of the cord, 
medulla, cerebellum, and basal ganglia terminate about 
the cells of the cortex. The cord, medulla, and cere- 
bellum are connected with the higher brain centers by 
the fibers of the cerebral peduncles (Figs. 90 and 100), 
which are separated into two parts by an elongated mass 
of gray matter, the substantia nigra. The dorsal part 
is known as the tegmentum, while the ventral part is the 
crusta. 

The fibers of the brain are of three kinds — the com- 



214 ELEMENTS OF MAMMALIAN ANATOMY. 

mis sural fibers, the projection fibers, and the association 
fibers. 

The first-named constitute the commissures of the 
brain previously described (Figs. 90, 92). In addition 
to these commissures, numerous other fibers cross to the 
opposite half in that portion of the brain caudad of the 
optic thalami. The internal portion of the medulla 




Fig. 100. — Diagram of Chief Fiber Tracts of the Mammalian Brain. 
Lateral Aspect. 

a, b, c, d, e, Fibers forming internal capsule; ac, anterior corpus quad- 
rigeminum; cb, direct cerebellar tract; cr, crossed pyramidal or 
chief motor tract; cs, cortico-pontine or secondary motor tract; m, 
middle peduncle of cerebellum; ng, nuclei gracilis and cuneatus; n, 
decussation of crossed pyramidal tract; o, optic thalamus; oc, optic 
chiasm; pc, posterior corpus quadrigeminum ; pons, transverse fibers 
of pons Varolii ; py, pyramids formed by pyramidal tract ; pi, posterior 
longitudinal bundle; rn, nucleus ruber; s, antero-lateral cerebellar 
tract; sn, substantia nigra; sp, superior cerebellar peduncle; st, 
corpus striatum ; t, fibers of the fillet or great sensory tract. 

oblongata possesses numerous transverse fibers which, 
with the longitudinal fibers, form a kind of reticulum 
in the midst of the gray matter, known as the jormatio 
reticularis. 

The projection fibers (Fig. 100) are those connecting 
the cortex with the lower brain centers and the cord. 
The chief motor tract is the crossed pyramidal tract 



THE NERVOUS SYSTEM. 215 

already described in the cord. It may be traced from 
the pyramids to its origin in the cortex in the region of 
the crucial sulcus (Fig. 89), by slicing away the ventral 
portion of the brain obliquely in a plane joining the 
cephalic margin of the pons and the crucial sulcus. Num- 
erous fibers are given off by this tract to the motor roots 
of the cranial as well as the spinal nerves. 

The secondary motor tract, cortico pontine tract, carries 
motor impulses from the frontal cortex to the medulla, 
whence other fibers convey them to the opposite half of 
the cerebellum. The axis-cylinders of the cells here 
transmit the impulses through the inferior peduncle to 
the cells in the anterior horn of gray matter of the cord. 

The great sensory tract of the brain is the fillet. Its 
fibers originate largely in the cells of the nuclei gracilis 
and cuneatus of the medulla (Figs. 98, 99, 100) and cross 
over to the opposite side of the medulla, forming the 
sensory or superior pyramidal decussation. This tract 
receives also fibers from the spinal cord, the cerebellum, 
and the medulla oblongata. 

These projection fibers, after leaving the peduncular 
region, turn dorsad to pass with others through the 
corpus striatum and laterad of the optic thalamus. In 
this part of their course they form what is known as the 
internal capsule (Fig. 95). The spreading out of the 
projection fibers just beneath the cortex of the cerebrum 
forms the corona radiata. 

The association fibers are those which connect different 
portions of the same cerebral hemisphere. Two kinds 
are recognized. The short fibers connect adjacent 
convolutions, while the long ones place in communication 
two remote portions of a hemisphere. 



2l6 ELEMENTS OF MAMMALIAN ANATOMY. 

PRACTICAL QUESTIONS AXD SUGGESTIONS. 

1. Describe the membranes of the cord. 

2. What difference in the size of the nerve roots in the various regions 
of the cord ? 

3. Draw a cross-section of the cord showing all features visible to 
the naked eye. 

4. How does the arrangement of the gray matter of the cord and 
brain differ? 

5. Describe the processes of nerve cells. 

6. In what portions of the body are nerve cells found? 

7. What is the location of the cells whose protoplasmic processes 
largely make up the tracts of Goll and Burdach ? 

8. What part of the cord is occupied by the chief motor tract? 

9. What tracts of the cord originate or terminate within the cere- 
bellum ? 

10. Describe the course of the crossed pyramidal tract throughout 
the axial nervous system. 

1 1 . Describe three bundles of commissural fibers in the brain. 

12. Which tract of the projection fibers contains the longest axis- 
cylinder processes? 

1 3 . Describe the great sensor}' tract of the brain. 

14. What do the association fibers connect? 

15. Tell what is known of the functions of various regions of the cortex. 

16. Explain why paralysis of the left side of the body would result 
from an injury to the right motor region of the cortex. 

17. Procure a piece of spinal cord from the butcher-shop. Smear 
a bit of the gray matter on a glass slip, dry, then stain in hematoxylin, 
wash, and after drying mount in balsam. Draw and describe nerve cells 
thus found. 



THE PERIPHERAL NERVES. 

All portions of the head, trunk, and limbs of the cat 
are supplied with nerve fibers which are in communication 
with the central nerA'ous system by means of fifty-two 
pairs of nerve bundles, forming what are known in the 
brain region as the cranial nerves and in the region of 
the cord as the spinal nerves. 

The Cranial Nerves. — There are twelve pairs of cranial 
nerves, all of which pass through foramina in the base 
of the skull, and all except one, the tenth or vagus, are 



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2l8 ELEMENTS OF MAMMALIAN ANATOMY. 

distributed to structures of the head and neck. They 
are divided according to function into motor and sensory. 
Some of the nerves communicate with the brain by more 
than one root, and in such cases the same nerve may have 
sensory fibers in one root and motor fibers in another. 
For example, the trigeminal nerve transmits a stimulus 
causing the muscles of mastication to contract and also 
supplies the teeth with sensory fibers (Fig. 90). 

The olfactory, optic, auditory and glossopharyngeal 
are the only cranial nerves wholly sensory. The oculo- 
motor, patheticus or trochlearis, abducens, facial, spinal 
accessory, and hypoglossal are wholly motor. The 
trigeminal and pneumogastric contain both motor and 
sensory fibers. 

The dissection of the cranial nerves is very difficult. 
A head, containing a brain hardened by a formalin in- 
jection, should be placed in 500 c.c. of 5% nitric acid, 
which will decalcify the bone in about a week. After 
washing out the acid by soaking the specimen in running 
water twenty-four hours, the dissector may with much 
care follow the course of the nerves peripherad from their 
origin at the base of the brain. The vagus nerve must 
of course be traced in an entire specimen, where it may 
be easily followed in the neck region along with the 
carotid artery, whence it passes to the lungs and stomach 
(Fig. 64). 

Some of the sensory nerve roots bear ganglia, the 
largest of which is the Gasserian ganglion, more than 
a half centimeter in diameter, forming a knot on the 
sensory root of the trigeminal, within the cranial cavity 
(Fig. 90). 

The Spinal Nerves. — There are forty pairs of nerves 
connected with the spinal cord. They issue from the 
vertebral canal through the intervertebral foramina. 



THE NERVOUS SYSTEM. 2lQ 

Each nerve is connected to the cord by a ventral and 
dorsal root (Figs. 90 and 98). The former is also known 
as the motor root, since its fibers are almost entirely 
motor, while the latter is the sensory root, as it is com- 
posed of fibers transmitting impulses to the central 
nervous system. A ganglion about the size of a pin- 
head is located on the dorsal root immediately proximad 
of its junction with the ventral root, within the inter- 
vertebral foramen. This anatomy can be displayed by 
cutting away the dorsal muscles on either side of the 
column, and then, with the bone-cutters, severing the 
laminae of several of the arches of the vertebrae, so that 
the roof may be removed from the vertebral canal (Fig. 
22). 

Immediately beyond the intervertebral foramen each 
nerve gives off a dorsal branch to the muscles of the 
back, and a small connecting twig to the sympathetic 
system. The main nerve is then spoken of as the ventral 
branch. These main nerves or ventral branches, in 
various regions of the trunk, anastomose with each other, 
forming plexuses. In the region of the neck there is 
formed the cervical plexus; in the region of the shoulder, 
the brachial plexus; in the region of the loins, the lumbar 
plexus; and in the region of the sacrum, the sacral plexus 
(Figs. 1 01 and 102). 

There are eight cervical nerves, the first of which does 
not make its exit through the intervertebral foramen, 
as do all the other spinal nerves, but traverses a foramen 
in the atlas. The first five cervical nerves, the three 
posterior cranial nerves, and branches from the sym- 
pathetic trunk, form the cervical plexus. These five 
cervical nerves supply mainly the structures of the neck. 

There are thirteen pairs of thoracic nerves. The 
ventral branches of the sixth, seventh, and eighth cervical 



220 



ELEMENTS OF MAMMALIAN ANATOMY. 



nerves and the first thoracic nerve form the brachial 
plexus. This may be displayed by removing the cephalo- 
humeral muscle and cutting through the pectoral muscles 




Fig. 101. — Ventral Aspect of the Brachial Plexus and Chief Nerves 

of the Arm. 
6, 7, 8, and 1, Sixth, seventh, and eighth cervical and first dorsal nerves; 

at, ath, anterior thoracic nerves ; a and b, to muscles of the forearm ; 

c and d, to the joint; ex, circumflex nerve; en, internal cutaneous; 

de, to the deltoid ; g, to the digits ; /, to the digits ; jo, supracondyloid 

foramen ; It, long thoracic ; mc, musculocutaneous ; me, median nerve ; 

pi, posterior interosseous ; pth, posterior thoracic ; sp, musculospiral ; 

sp, to suprascapular region ; sb, to subscapular region ; ex, subscapular ; 

ra, radial ; un, ulnar nerve. 



THE NERVOUS SYSTEM. 221 

about two centimeters from their origin (Fig. 47). The 
manner in which the nerves anastomose varies some- 
what, but the following will be found approximately 
correct : 

The sixth cervical nerve gives off a small branch to 
the rhomb oideus and levator anguli muscles of the 
shoulder, and then divides into two nearly equal 
branches, one of which supplies the muscles on the 
lateral aspect of the scapula, and the other joins with 
the seventh cervical nerve. Small branches from the 
fifth and sixth cervical nerves unite to form the phrenic 
nerve supplying the diaphragm. 

The seventh cervical nerve gives off three small 
branches at about the same point, one of which is the 
posterior thoracic supplying the serratus magnus muscle, 
a second helps to form the musculocutaneous, and the 
third forms part of the median and anterior thoracic. 
The main portion of the seventh cervical unites with the 
eighth and first thoracic, to form the musculo spiral nerve. 
The circumflex and subscapular branches supplying the 
deltoid and subscapular muscles are also derived from the 
seventh. 

The eighth cervical nerve, after giving off a small 
branch to the pectoral muscle, a small twig to the median 
nerve, and a large branch to the first thoracic nerve, 
is continued as the main part of the musculospiral nerve. 

The first thoracic nerve gives first a large branch 
to the musculospiral nerve, a second small branch to 
the anterior thoracic, and a third branch forming the 
internal cutaneous nerve supplying the skin of the arm 
and forearm on the caudal aspect. The main portion 
of the first thoracic nerve then continues as the main part 
of the ulnar nerve. 

The nerves of the forelimb are five in number (Fig. 



2 22 ELEMENTS OF MAMMALIAN ANATOMY. 

101): the external cutaneous, the internal cutaneous, 
the musculospiral, the median, and the ulnar. The 
external cutaneous arises from the sixth and seventh 
cervical nerves and passes distad along the caudal aspect 
of the biceps to the cephalic aspect of the forearm, where 
it becomes subcutaneous. It supplies the biceps and 
coracoid muscles and the skin of the forearm. The 
internal cutaneous arises from the first thoracic and 
passes along the ventral side of the arm, becoming 
subcutaneous just proximad of the elbow, where it is 
distributed to the skin of the arm and forearm on the 
caudal and ventral aspects. 

The musculospiral arises from the seventh and eighth 
cervical and first thoracic nerves. It is the largest 
component of the brachial plexus. It winds obliquely 
around the humerus to the cephalic aspect, where it 
divides into two branches, the radial and the posterior 
interosseous. The radial nerve is the smaller and be- 
comes subcutaneous near the elbow, and passes along 
the radial region. The posterior interosseous proceeds 
along the dorsal aspect of the forearm to the wrist, 
where it divides into branches supplying the digits. 

The median nerve arises from the seventh and eighth 
cervical and first thoracic. It follows the course of 
the brachial artery, passing through the supracondylar 
foramen to the elbow, where it passes beneath the pro- 
nator teres to the carpal region, and supplies the first, 
second, and third digits. It also supplies the pronator 
teres and flexor muscles of the forearm. 

The ulnar nerve (Fig. 101) is derived from the eighth 
cervical and first thoracic. It courses with the brachial 
artery to the middle of the humerus, where it turns 
caudad to pass between the olecranon process and 
internal condyle of the humerus. It is here sub- 



THE NERVOUS SYSTEM. 223 

cutaneous and furnishes the sensation experienced when 
one strikes what is popularly called his "funny bone," 
but what is really the ulnar nerve. It then passes 
down the ulnar side of the forearm, supplying some 
of the flexor muscles, and finally divides to supply 
the fourth and fifth digits. The ventral branches 
of the remaining thoracic nerves encircle the body, 
supplying the muscles and skin of those regions. 

The lumbar plexus (Fig. 102) is composed of the 
anastomosing of the ventral branches of the seven 
lumbar nerves. As in the cervical and thoracic nerves, 
the lumbar nerves divide into dorsal and ventral branches 
immediately without the intervertebral foramen. The 
former supply the muscles and skin of the back. The 
first five ventral branches are joined to each other by 
a delicate nerve-cord. In order to display this plexus, 
the entire ventral and lateral abdominal wall should 
be cut away and the specimen securely nailed to the 
tray on its back. The adipose tissue and muscles lying 
on either side of the bodies of the lumbar vertebrae 
must be carefully picked away until the roots of the 
nerves are apparent. They may then be easily followed 
distad. 

The iliohypogastric nerve is the ventral branch of 
the first lumbar nerve. It supplies the muscles of 
the abdomen. This nerve and the two next described 
are scarcely as large in diameter as an ordinary pin. 
The ilio-inguinal nerve is the ventral branch of the 
second lumbar nerve. Within two centimeters of its 
origin it divides into two branches, the cephalic of 
which supplies the rectus and transverse muscles and 
the caudal supplies structures in the inguinal region. 
The lumbo -inguinal nerve is the ventral branch of the 
third lumbar nerve. Its cephalic branch supplies the 



2 24 ELEMENTS OF MAMMALIAN ANATOMY. 

lumbar region and its caudal branch is distributed 
to the superficial structures of the inguinal region. The 
fourth lumbar nerve divides into two parts, one of which 
is the external cutaneous nerve, supplying the skin and 
other structures of the hip region, and the other is the 
external spermatic, supplying the external genital organs. 

The anterior crural nerve is composed mainly of branches 
of the fifth and sixth lumbar. It receives a small branch 
from the fourth. It supplies the psoas muscles, which 
it pierces, and then divides into several branches, one 
of which is the saphenous, passing subcutaneously along 
the mesal aspect of the leg. The other nerves supply 
the muscles of the thigh on the cephalic and mesal 
aspect. The obturator nerve is composed of branches 
from the sixth and seventh lumbar. It is smaller than 
the preceding, and passes through the obturator foramen 
to supply the obturator and adductor muscles. 

The great sciatic nerve is composed mainly of the 
ventral branches of the seventh lumbar and first sacral 
nerves. It usually receives accessions from the other 
sacral nerves and the sixth lumbar. The great sciatic 
is the largest peripheral nerve in the body. It passes 
caudad from its origin around the greater sciatic notch 
and thence along the caudal aspect of the thigh to the 
popliteal space, where it divides into the internal and 
external popliteal nerves. The former continues down 
the caudal side of the tibia as the posterior tibial nerve 
to the internal malleolus, where it divides into internal 
and external plantar nerves, which supply the digits. 
The external popliteal or peroneal nerve extends to 
the outer cephalic aspect of the leg, where it divides 
into the musculocutaneous and anterior tibial nerves. The 
former extends between the extensor longus digitorum 
and peronei muscles to its ramification on the dorsum 



THE NERVOUS SYSTEM. 



225 




Fig. 102 — Ventral Aspect of the Nerves of Hind-limb. 
5, 6, 7, 1, 2, and 3, Fourth, fifth, sixth, and seventh lumbar, and first, 
second, and third sacral nerves ; a, branch from the fourth to the fifth ; 
ac, anterior crural; cu, saphenous; d, anterior tibial; e, peroneal or 
musculocutaneous; ex, external popliteal or peroneal; ef, external 
plantar; jo, obturator foramen; gs, greater sciatic; g, external sper- 
matic ; it, internal popliteal ; ip, internal plantar ; kn, knee ; /, external 
cutaneous; Is, lumbosacral cord; t, posterior tibial; s, small sciatic. 

19 



226 ELEMENTS OF MAMMALIAN ANATOMY. 

of the foot. It supplies the skin along its course and 
the peronei muscles. The anterior tibial nerve passes 
down on the cephalic aspect of the tibia beneath the 
extensor longus digit orum muscle to the tarsal region, 
where it anastomoses with a branch of the external 
cutaneous, and supplies the skin, tibialis anticus, and 
the extensor muscles. 

The lesser sciatic nerve is a branch of the greater 
sciatic in the buttock region. The pyriformis, obturator, 
gemelli, quadratus femoris, semitendinosus, and semi- 
membranosus muscles are innervated by the greater 
sciatic nerve (Figs. 48 and 102). 

The sacral plexus is an irregular network composed 
of the ventral branches of the three sacral nerves and 
two or more small twigs from the seventh lumbar (Fig. 
102). This plexus is seldom the same in any two cats. 
From it are given off the internal pudic and glutei nerves. 
The former supplies the prostate and anal glands, the 
sphincter muscle, and the penis. The latter supplies 
the glutei and pyriformis muscle. 



THE SYMPATHETIC NERVOUS SYSTEM. 

The sympathetic nervous system is composed chiefly 
of a pair of nerve-cords extending from the base of the 
skull to the root of the tail, a number of ganglia and 
branches supplying the thoracic and abdominal viscera, 
and numerous minute fibers supplying the muscular 
walls of the blood-vessels in all parts of the body. The 
sympathetic "system supplies all non-striped or involun- 
tary muscles in any part of the body. 

In order to demonstrate this system successfully, one 
should use a lean injected specimen. After the cat has 
been securely nailed on its back to the tray, the entire 



THE NERVOUS SYSTEM. 227 

ventral half of the thoracic and abdominal walls should 
be removed. By pushing the heart and lungs to the 
left side a white cord about one millimeter in diameter 
may be seen lying near the median dorsal line (Fig. 103). 
The left cord may be found in a similar manner and 
both followed cephalad and caudad, noting their numer- 
ous branches in accordance with the following descrip- 
tion. 

The sympathetic nerve=cord begins in the superior cervi- 
cal ganglion lying near the arigle of the mandible, beneath 
the submaxillary and lymphatic glands. This ganglion 
is about the shape of a grain of wheat, but not more 
than half so large, and is adjacent to the small vagus 
ganglion on the dorsal side of the carotid artery. The 
ganglia are masses of large nerve cells and occur at regular 
intervals on the sympathetic cords in the body cavity, 
and are present also on some of the branches of the 
cords (Fig. 104). On the cords there are three pairs 
of cervical ganglia, thirteen pairs of thoracic ganglia, 
seven pairs of lumbar ganglia, and one or two pairs of 
sacral ganglia, in addition to two median unpaired 
sacral ganglia. 

In the cervical region the sympathetic and pneumo- 
gastric, or tenth cranial nerve, are bound in a common 
sheath lying along the lateral aspect of the carotid 
artery. One or two centimeters cephalad of the first 
rib is the thyroid or middle cervical ganglion, whence the 
nerve proceeds in two cords, enclosing the subclavian 
artery, to the large inferior cervical ganglion just caudad 
of the first rib. From the cervical portions of the sym- 
pathetic cord are given off numerous delicate branches, 
forming the carotid plexus on the carotid artery, and 
uniting with the eight posterior cranial nerves and the 
first spinal nerve. From the inferior cervical ganglion 



228 



ELEMENTS OF MAMMALIAN ANATOMY. 



a branch goes to the vagus nerve, several branches 

to the brachial plexus, and 
a branch to the heart, form- 
ing the cardiac plexus, while 
the main sympathetic cord 
continues along the dorsal 
thoracic wall. A ganglion 
occurs opposite each verte- 
bral body, from which it 
gives off a branch to the 
corresponding spinal nerve. 
The great splanchnic arises 
from the main cord just 
cephalad of the diaphragm 
and extends to a group of 
ganglia in the region of the 
trunk of the coeliac axis 




Fig. 103. — Chief Part of Left 
Half of Sympathetic System 
Cephaead of the Diaphragm. 
Semi diagrammatic. 
5, 6, 7, 8, 9, and 10, Fifth, sixth, 
seventh, and eighth cervical 
nerves, and first and second 
thoracic spinal nerves; a, the 
dorsal branch of the left vagus 
In; an, dorsal branch of the right 
vagus ; ax, common dorsal vagus 
formed by a and an; avb, ventral 
vagus ; be, cardiac branch of sg, cr, 
carotid plexus; car, carotid ar- 
tery ; cm, rami communicantes ; cp, 
cardiac plexus; dia, diaphragm; 
g, ganglia in the thoracic cavity ; 
ig, middle cervical ganglion; Ig, 
portion of left lung ; In, left vagus 
nerve; nv, cranial nerve; pn, 
phrenic nerve; pp, pulmonary 
plexus ; sn, sympathetic cord ; sm, 
superior cervical ganglion ; sb, left 
subclavian artery; sg, stellate ganglion or inferior cervical; spm, splanch- 
nic major nerve; vg, vagus ganglion; v, vagus nerve. 



THE NERVOUS SYSTEM. 



229 



(Figs. 103 and 104). These ganglia and anastomosing 
branches constitute the solar or epigastric plexus, lying 




Fig. 104. — Chief Part of Left Half of Sympathetic System Caudad 
of THE Diaphragm. Semidiagrammatic. 

bl, Bladder; ce, coeliac axis; du, duodenum cut off; dia, diaphragm; gr, 
anterior gastric plexus; g, ganglion; im, inferior mesenteric artery; 
il, external iliac artery; ng, dorsal branch of vagus (Fig. 103, ax); 
nl, ventral branch of vagus ; oe, esophagus cut off ; p, superior mesen- 
teric plexus; plx, inferior mesenteric plexus; px, branches to dorsal 
gastric plexus; rn, renal plexus; sm, superior mesenteric artery; spn, 
splanchnic major or greater splanchnic nerve from the sympathetic 
cord ; sg, semilunar ganglion ; spc, sympathetic cord of left side. 



dorsad of the stomach, to which it sends numerous 
branches. This plexus also receives the lesser splanchnic 
nerve coming from the sympathetic cord just cephalad 



230 ELEMENTS OF MAMMALIAN ANATOMY. 

of the diaphragm, and branches from the tenth cranial 
nerve. 

The largest ganglion of the solar plexus is the semi- 
lunar. The solar and its allied plexuses send nerves 
to the diaphragm, suprarenal bodies, many of the blood- 
vessels of the abdominal cavity, stomach, kidneys, 
ureters, testes or ovaries, uterus, liver, gall-bladder, 
spleen, pancreas, and intestines. 

The hypogastric plexus is the third great sympathetic 
plexus. It lies on the ventral aspect of the two caudal 
lumbar vertebrae and is formed by branches from the 
solar plexus and a few twigs from the sympathetic 
cords. It supplies the blood-vessels of the pelvic region 
and all the organs of the pelvis. The sympathetic cords 
in the lumbar region lie near together and the com- 
municating branches between them and the spinal 
nerves are longer than in the thoracic region. In the 
sacral region there are no rami communicantes, and the 
ganglia are irregularly arranged. A median ganglion 
in the sacral region is known as the ganglion impar. 
There may be two median ganglia. The sympathetic 
cords terminate in the tail. 



PRACTICAL QUESTIONS AND SUGGESTIONS. 

1. Name the foramina of the skull giving passage to one or more 
cranial nerves. 

2. From a study of one or more specimens and the description in the 
book make a diagrammatic drawing of each cranial nerve. 

3. Which cranial nerves have their roots in the medulla? 

4. Name the cranial nerves which are wholly motor. 

5. Which of the cranial nerves do not supply structures of the head? 

6. Of what are ganglia composed ? 

7. Make a drawing of your dissection showing the connection between 
the spinal and sympathetic nerves. 

8. Which spinal nerves form the several plexuses? 

9. Make a drawing showing wherein the brachial plexus in your 
specimen differs from that described in the text. 



THE NERVOUS SYSTEM. 23 1 

10. Write a description of your dissection of the nerves of the thoracic 
limb. 

11. Mention in what way the lumbar plexus differs from the descrip- 
tion in the book. 

12. Draw the great sciatic nerve and its branches as seen from the 
caudal aspect. 

13. What nerves supply the digits? 

14. Describe the chief plexuses of the sympathetic system. 

15. How do stimuli from the viscera reach the brain? 

16. What portion of the body is not supplied with nerves from the 
sympathetic system? 



THE ORGANS OF SENSE. 

The organs of sense are the specialized peripheral 
terminations of the sensory nerves, and are so constructed 
as to be capable of receiving only a certain kind of 
stimulus. The stimuli for the eye are ether vibrations; 
those for the ear are vibrations of the air. The stimu- 
lation of the sensory nerves produces sensations in the 
cells of the cerebral cortex to which they lead. 

The external stimuli giving rise to the internal sen- 
sations of seeing, hearing, smelling, and tasting are 
transmitted by only four pairs of cranial nerves, while 
the stimuli of cutaneous sensations are transmitted 
by three pairs of cranial nerves and all the spinal nerves. 

Cutaneous Sense Organs. — The cutaneous sense organs 
are composed of the endings of the sensory nerves in 
all parts of the skin and the mucous membrane of the 
mouth, nose, arms, vagina, and urethra. One kind of 
sense organs, those of pain, are present in every organ of 
the body. The sense organ of pain is probably an 
unmodified free nerve-ending. 

While all portions of the skin and perhaps other 
parts of the body are supplied with organs capable of 
receiving stimuli giving rise to tactile sensation, the 
soles of the feet and the skin at the base of the vibrissae 



232 



ELEMENTS OF MAMMALIAN ANATOMY. 



are specially sensitive regions. The nerves terminate 
in a kind of wreath formation about the base of the 
vibrissas. 

All of these sense organs are invisible to the naked 
eye except the Pacinian corpuscles, whose function is 
unknown. If the mesentery is held up and looked 
through toward the light, the Pacinian corpuscles or 
sensory nerve terminations appear as translucent oval 
bulbs about two millimeters long. If a piece of the 
mesentery containing a corpuscle is 
pinned tense on a piece of cork and 
then cut out and placed ten minutes 
in 3% acetic acid, the termination of 
the nerve within the corpuscle may 
be seen with a microscope magnifying 
thirty diameters. All the spinal sen- 
sory nerve fibers enter the cord by the 
posterior root (Figs. 90 and 96). 

The Olfactory Organ. — The organ of 
smell lies in that part of the mucous 
membrane lining the caudal part of 
the nasal cavity and the basal third of 
the ethmoturbinal bones (Fig. 18). 
That part of the mucous membrane 
containing the olfactory cells is known 
as the Schneiderian membrane. In a fresh specimen it is 
of a grayish color while the other mucous membrane is 
red. The first pair of cranial nerves convey the olfactory 
impulse to the brain. They pass through the foramina in 
the cribriform plate of the ethmoid bone, to the olfactory 
bulbs, from each of which two roots extend to the base 
of the cerebrum (Fig. 90). 

The Gustatory Organ. — The organ of taste is located 
chiefly in the mucous membrane on the dorsum of the 




Fig. 105. — Pacinian 
Corpuscle from 
the Mesentery, x 
20. 

ax, Axis-cylinder ; n, 
neurilemma; m, the 
white substance of 
Schwann; e, epithe- 
lial cell. 



THE NERVOUS SYSTEM. 233 

tongue, the soft palate, the pillars of the fauces, epi- 
glottis, and part of the cheek. On the dorsum of the 
tongue are seen four kinds of papillae — the circumvallate , 
the fungiform, the filiform, and flat. The circumvallate 
papillae are from eight to twelve in number, forming two 
sides of a triangle on the caudal portion of the dorsum 
of the tongue. The fungiform are blunt papillae scattered 
sparsely in the midst of the numerous filiform or pointed 
papillae (Fig. 55). The special organs of taste, known 
as taste-buds, are very numerous in the fungiform and 
circumvallate papillae of most mammals, but in the cat 
they are few and not well differentiated. These taste- 
buds occur in many parts of the mucous membrane of 
the mouth cavity, each being supplied with a branch 
of the glossopharyngeal nerve. 

The Visual Organ. — The special organ of sight is 
the eye, which occupies the orbital cavity of the skull. 
The ball of the eye is protected above and below by 
extensions of skin called the eyelids or palpebrae, which 
are lined with mucous membrane, a transparent layer 
of which, known as the conjunctiva, extends over the 
front of the eyeball between the two lids. The dorsal 
lid is raised by the levator palpebrae muscle, which 
has its origin in the occipitofrontalis muscle. A sphincter 
muscle, the orbicularis palpebrarum, lies on the margin 
of the lids, and by its contraction closes the eye. 

The point on either side where the two eyelids meet 
is termed the canthus or angle. At the mesal or inner 
canthus are two minute apertures, the puncta lachry- 
malia, leading into two short canals which unite to 
form the nasal duct. The lachrymal canal, which forms 
the channel for this duct, is clearly visible in the lach- 
rymal bone of the dried skull. At the mesal canthus 
there is a prominent fold of mucous membrane, the 



234 ELEMENTS OF MAMMALIAN ANATOMY. 

membrana nictitans, or plica semilunaris, which is a 
rudimentary structure in the cat, but is found well 
developed in birds, which have the power of sweeping 
it rapidly across the eyeball, thereby removing dust. 

On the inner surface of each lid are the Meibomian 
glands. The lachrymal gland lies in the dorso-lateral 
region of the orbit, and its ducts open on the ventral 
surface of the upper lid, whence the tears flow over 
the conjunctiva ventrad to the puncta lachrymalia. 
The Harderian gland is the very small gland at the mesal 
canthus. 

The muscles controlling the movements of the eye- 
ball are seven in number: four are recti muscles, two 
are oblique, and one is a retractor. The recti muscles 
(Fig. 90) originate on the bone around the optic for- 
amen, and are inserted on the sclerotic coat, caudad 
of the equatorial ring. The external rectus is inserted 
on the lateral aspect; the internal rectus, on the mesal 
aspect; the superior rectus, on the dorsal aspect; and 
the inferior rectus on the ventral aspect. The superior 
oblique muscle arises from the sphenoid bone mesad 
of the optic foramen, extends along the mesal wall of 
the orbital cavity to its dorso-mesal margin, where 
it passes through a tendinous loop fastened to the frontal 
bone and then turns laterad to its insertion in the sclerotic 
beneath the superior rectus. The inferior oblique arises 
from the lachrymal bone and is inserted on the sclerotic 
between the external and inferior recti muscles. The 
above muscles may be demonstrated by cutting away 
the lateral and dorsal walls of the orbital cavity. The 
retractor oculi originates on the boundary of the optic 
foramen and is inserted into the sclerotic around the 
entrance of the optic nerve. This muscle is completely 
hidden by the recti muscles. 



THE NERVOUS SYSTEM. 



235 



The eyeball is composed of three membranes and 
three humors. The outer coat, the sclerotic, consists 
of the opaque portion forming the caudal two-thirds, 
and the transparent portion, or cornea, forming the 
remainder (Fig. 106). The optic nerve pierces the 
sclerotic a little mesad of the longitudinal axis of the 
eye. The surface of the cornea is more strongly curved 
than that of the opaque portion of the sclerotic, and 




Fig. 106. — Longitudinal Section of the Eye. 
aq, Aqueous humor; c, cornea; cp, capsule of the lens; ch, choroid; ci, 
ciliary process; i, iris; Ig, ligament of lens; m, ciliary muscle; opn, 
optic nerve ; rt, retina ; sc, sclerotic coat ; os, ora serrata. 



contains no blood-vessels. The second or middle coat 
of the eye is formed by the choroid membrane and its 
extension, the iris. This coat is incomplete, as there 
is an aperture, the pupil, through the iris for the ad- 
mission of light. The choroid appears as a jet-black 
membrane, less than half as thick as the sclerotic, lying 
closely appressed to the latter. The choroid is lined 
internally by dark pigment cells, except in the caudal 
area around the optic nerve, which has a metallic luster. 



236 ELEMENTS OF MAMMALIAN ANATOMY. 

This portion is called the tapetum. It causes the shining 
appearance of the cat's eyes in the dark. The choroid 
is a vascular membrane, being supplied by the ophthalmic 
artery, a branch of the internal carotid. 

The iris is attached by its peripheral margin to the 
sclerotic and choroid coats, and hangs free in the aqueous 
humor. It gives color to the eye. In the cat it is 
yellowish, while in man it is frequently blue or black. 
The iris is merely a curtain to regulate the amount of 
light admitted to the retina. There is a sphincter 
muscle lying in it, which by contraction renders the 
pupil very small. There is probably no dilating muscle 
of the iris present in the cat. The short, v thickened, 
radial projecting folds of the choroid are the ciliary 
processes, which contain numerous blood-vessels, and 
in some mammals a gland. The ciliary muscle arises 
from the sclerotic coat near its junction with the cornea, 
and is inserted into the cephalic part of the choroid coat. 

The inner membrane of the eye is the retina, which is 
of a light gray color in a fresh specimen and seems quite 
free from the choroid. It is thickest in the caudal 
two-thirds of the cavity of the eyeball (Fig. 106). At 
the base of the ciliary bodies it seems to end with a 
free margin, called the ora serrata. In reality it becomes 
very thin here and is prolonged over the ciliary bodies 
and covers the caudal aspect of the iris. The blind 
spot is the point of entrance of the optic nerve, laterad 
of which is the yellow spot, or macula lutea, containing 
the fovea centralis, or acute point of vision. This is 
the point on which the rays of light are focused when 
the cat sees distinctly. 

The three humors of the eye are the aqueous, the 
crystalline lens, and the vitreous humor. The aqueous 
humor is a watery fluid occupying the anterior chamber 



THE NERVOUS SYSTEM. 237 

between the cornea and crystalline lens. It always 
escapes as soon as the cornea is punctured. The vitreous 
humor is of a jelly-like consistency, filling the large pos- 
terior chamber caudad of the lens. It is perfectly trans- 
parent and is surrounded by a delicate capsule, the 
hyaline membrane. 

The crystalline lens is a transparent biconvex tissue 
having a vertical diameter of about one centimeter 
and a shorter diameter through its optical axis. It 
is enclosed in a transparent elastic capsule, some of 
whose fibers are continued peripherad as the suspensory 
ligament which is inserted in the choroid coat (Fig. 106). 

The Auditory Organ. — The organ of hearing is com- 
posed of three parts — the external ear, middle ear, and 
internal ear. The first consists of the pinna and the 
auditorius meatus externus. The pinna is the pro- 
jecting portion of the ear capable of being moved by 
muscles, and is composed of integument strengthened 
by fibrocartilage. The auditorius meatus externus ex- 
tends from the base of the pinna to the tympanic mem- 
brane (Fig. 107). Its outer or lateral third is formed 
by cartilage, and the remainder by the tympanic por- 
tion of the temporal bone (Fig. 17). The meatus is 
lined with mucous membrane in which are numerous 
sebaceous and oleaginous glands. The latter secrete 
the wax of the ear. 

The middle ear, or tympanum, is an irregular cavity 
about one centimeter in diameter contained in the 
lateral chamber of the bulla (Fig. 107). It is separated 
from the external auditory meatus by the delicate 
translucent membrane, the membrana tympani. The 
petrous bone containing the internal ear forms part of 
the inner or nasal wall. In the petrous bone are two 
foramina which may be seen in a dry skull by looking 



2 3 8 



ELEMENTS OF MAMMALIAN ANATOMY. 




through the external auditory meatus. The more dor- 
sal foramen is the fenestra ovalis, which in the recent 
state is closed by a membrane to which the foot of the 
stapes is attached. The ventral one is the fenestra 
rotundum, also closed by a membrane in the recent 
state. In the dry skull the fenestra ovalis opens into 
the first or basal whorl of the cochlea, and the fenestra 

rotundum opens into the vesti- 
bule of the internal ear. The 
Eustachian tube (Fig. 18), whose 
opening may be seen cephalad of 
the auditory bulla, connects the 
middle ear with the posterior 
nares and thus admits air to the 
tympanic cavity. 

To demonstrate further the 
anatomy of the middle ear, one 
should clean the flesh from a 
fresh or preserved head and care- 
fully cut away the ventral walls 
of both chambers of the auditory 
bulla (Fig. 17). 

In the middle ear are three 
bones, the malleus, incus, and 
stapes, commonly called ham- 
mer, anvil, and stirrup. They 
form a crooked chain across the cavity. The long process 
of the malleus is fastened throughout nearly its whole 
length to the inner or mesal surface of the membrana 
tympani, and its enlarged extremity articulates with the 
body of the incus. The latter has two legs, to one of 
which the stapes is attached. The base of the stapes is 
inserted in the membrane closing the fenestra ovalis (Figs. 
17 and 107). 



Fig. 107. — Diagram of the 
Mammalian Ear. 

The internal ear is repre- 
sented removed about a 
centimeter from the mid- 
dle ear and slightly rotated 
to the left. The base of the 
stapes, s, in nature, covers 
the fenestra ovalis, ov; c, 
basal whorl of the cochlea ; 
ea, external auditory meat- 
us ; eu, opening of the Eu- 
stachian tube; i, incus; in, 
malleus ; sc, semicircular 
canals; ve, vestibule; t, 
tympanum. 



THE NERVOUS SYSTEM. 



2 39 



The internal ear, or labyrinth, consists of three parts — 
the vestibule, cochlea, and semicircular canals (Figs. 
1 8 and 107). All of these parts are of membrane and 
lie in cavities of corresponding shape within the petrous 
bone. A lymphoid fluid, the perilymph, floats the deli- 
cate membranous internal ear within its bony cavity, 
while within the membrane is a similar fluid, the endo- 
lymph. The vestibule is a small sac adjacent to the 
tympanum, and may be seen by looking through the 




Fig. 108. — Section of the Cochlea op the Calf. X 10. — {From 
Kile nber ger, after Kolliker.) 

a, Modiolus; c, scala tympani; v, scala vestibuli; Im, lamina spiralis; pt, 
portion of the petrous bone; r, scala media, or ductus cochlearis. 



fenestra ovalis. From the dorso-caudal aspect of the 
vestibule, arch three semicircular canals at nearly right 
angles to one another. The external semicircular canal 
is in a horizontal plane and surrounds a small fossa 
almost caudad of the fenestra ovalis. The superior 
semicircular canal lies in a transverse plane caudad 
to the preceding. The posterior semicircular canal 
lies in a vertical longitudinal plane, immediately laterad 
from the jugular foramen. 

The cochlea is a coiled canal lying within the coiled 



240 ELEMENTS OF MAMMALIAN ANATOMY. 

cavity, the bony cochlea, extending cephalad from the 
vestibule. If both chambers of the auditory bulla are 
removed and a bristle thrust into the fenestra rotundum 
(Fig. 17), it will enter the basal whorl of the bony cochlea. 
A line drawn from the lateral margin of the foramen 
ovale to the mesal margin of the fenestra rotundum 
passes through the apex and middle of the base of the 
cochlea, which may be rendered visible by carefully 
clipping off with the bone-forceps the ventral portion 
of the petrous bone along the line indicated. This 
coiled canal, the cochlea, is divided into two channels 
by a shelf of bone, the lamina spiralis, projecting from 
the central axis or modiolus of the coil (Fig. 109). The 
bony lamina extends but partly across the canal, the 
remaining distance being bridged by membrane. The 
cephalic channel, or the one nearer the apex of the 
cochlea, is called the scala vestibuli. The other is 
the scala tympani. 

The semicircular canals probably have nothing to do 
with hearing, as they are well developed in fishes, which 
do not hear at all. They may aid in helping the cat to 
maintain its equilibrium. The auditory nerve, how- 
ever, is distributed to the vestibule and semicircular 
canals as well as to the cochlea upon the lamina spiralis, 
where the organ of Corti, the essential organ of hearing, 
is located. 



REMARKS ON THE MAMMALIAN NERVOUS SYSTEM. 
So far as known, the relation of the sympathetic to the 
peripheral and central nervous systems is the same in 
all mammals. The number of spinal nerves varies with 
the number of vertebrae. The distribution of these 
nerves, however, is approximately the same in all forms 



THE NERVOUS SYSTEM. 241 

with five digits. In those having a less number of digits 
the nerve branch corresponding to the lacking digit 
or digits is wanting. The arrangement of the columns 
or tracts of fibers in the spinal cord is very similar in 
all the orders. The anterior or direct pyramidal tract, 
however, is absent in most orders below the Primates. 
It is best developed in man, although in a number of 
cases it has been found entirely wanting in the human. 
The number of the cranial nerves is always twelve and 
their distribution is the same in all forms investigated. 

The structure of the brain in the Ornithodelphia and 
Didelphia differs considerably from that of the Mono- 
delphia. In the two former subclasses the corpus 
callosum and fornix are very rudimentary, but the 
anterior commissure piercing the corpora striata is un- 
usually large. The fibers, which in the Monodelphia 
arise from the cells of the hippocampus, and extend 
cephalad to form the fornix, cross transversely to the 
opposite hippocampus in the two lower subclasses. 

In all higher mammals the cerebrum is greatly con- 
voluted, but in the lower ones the convolutions are 
few or almost absent, as in Ornithorhynchus. The 
above-mentioned features show that the ornithodelphian 
brain presents a striking similarity to the brains of 
reptiles and birds. The brains of Rodentia possess but 
few convolutions, while the brain of man is the most 
highly convoluted. 

The size of the brain varies widely. As a rule, the 
larger the brain in proportion to the size of the animal, 
the greater is its intelligence. However, in man this 
statement does not hold true, as an individual with a 
small brain may be much more capable mentally than 
one with a large brain. Mental power in man seems 
to depend upon the development of the cells and fibers 
of the brain. 



242 ELEMENTS OF MAMMALIAN ANATOMY. 

The average weight of a male human brain is about 
three pounds; of a female, about two and two-thirds 
pounds. The human brain is -j^ the weight of the body; 
the ape's, 2V; the rat's, ¥ V ; the sheep's, gi T ; and the ele- 
phant's, g-J-Q. The brain of man is larger than that of 
any other mammal except the whale and elephant. The 
brain of a large whale weighs over four pounds, while 
that of a large elephant will weigh about ten pounds. 

PRACTICAL QUESTIONS AND SUGGESTIONS. 

1. How many nerves transmit the stimuli received by the organs of 
special sense? 

2. Where are the sense organs of pain located ? 

3. How many sense organs are visible in the mesentery of your 
specimen? 

4. Describe the path of a stimulus from the index finger to the brain. 

5. Through which nerve roots would the stimuli received by the 
cutaneous sense organs pass into the cord? 

6. Describe the nerves transmitting the stimuli from the olfactory 
organ. 

7. Describe the gland secreting the tears and how they reach the 
nasal cavity. 

8. By cutting away the lateral and dorsal walls of the orbit dissect 
the muscles of the eyeball and make a drawing of them, labeling all parts. 

9. What nerves control the movements of the eyeball? 

10. Procure the eyes of any mammal from the butcher-shop or slaughter- 
house ; bisect one in the meridional and the other in the equatorial direc- 
tion. Make a drawing of the features seen and label. 

11. Remove the crystalline lens from a fresh eye, describe its size, 
shape, structure, length of focus, and power of magnification. 

12. Describe the path of a stimulus from the retina to the area of 
sight in the brain. 

13. Name every feature visible in the eyes you have dissected. 

14. What nerve supplies the auditory organ? 

15. Describe the middle ear. 

16. In what part of the temporal bone is the internal ear located? 

17. By looking into the auditorius meatus of the dried skull two open- 
ings are seen. Into which portions of the internal ear do these lead? 

18. Write a description of the internal ear. 

19. Mention some important points of difference in the nervous system 
of various mammals. 

20. What relation, if any, between intellectual ability and brain devel- 
opment? 



NDEX 



A. 

Abdominal aorta, 144 

arteries, 145 

cavity, 125 

muscles, 104, 106 

veins, 154 
Accessory glands, 131 
Acetabulum, 79, 81 
Adipose tissue, 33 
Air sacs, 172 

Alcohol as a preservative, 27 
Alimentary canal, 124 

length of, in mammals, 13' 
Alveoli, 172 
Amphiarthroses, 89 
Amphibia, 19 
Anesthetization, 21, 22 
Anatomy, 17 

Anterior perforated space, 191 
Aorta, 143 
Aponeuroses, 95 
Aqueduct of Sylvius, 193 
Arachnoid, 186, 205 
Arbor vitae, 203 
Arm, arteries of, 148 

bones of, 67 

muscles of, 100 

nerves of, 222 
Arteries, 143 

abdomen, 144 

arm, 148 

brain, 146 

injection of, 20 

leg, 151 

neck, 145 

thorax, 143 

valves of, 154 
Artery, adrenolumbalis, 145 

anastomotica magna, 150 

axillary, 148 

basilar, 146 

brachial, 148, 150 



Artery, bronchial, 144 
carotid, 143, 146 
cerebellar, 146 
cerebral, 146 
circumflex anterior, 150 
cceliac, 144 
coronary, 143, 145 
epigastric, 151 
femoral, 151 

anterior, 151 

posterior inferior, 152 

superior posterior, 151 
hepatic, 144 
iliac, 145 
iliolumbar, 145 
inferior alveolar, 147 
infraorbital, 147 
intercostal, 148 
interosseous, 150 
lingual, 147 
lumbar, 144 
malleolar, 153 
mammary, 148 
maxillary, 147 
meningeal, 147 
mesenteric, 145 
ophthalmic, 147 
phrenic, 145 
popliteal, 152 
profunda, 151 

superior, 150 
pulmonary, 142 
radial, 148, 150 
renal, 145 
saphenous, 152 
spermatic, 144 
subclavian, 143, 148 
subscapular, 149 
temporal, 147 
thoracic, 149 
thyroid, 147 

axis, 149 
tibial, 152 



243 



244 



INDEX. 



Artery, ulnar, 150 

vertebral, 147 

volar, 150 
Articulation, 40 
Arytenoid cartilage, 169 
Association fibers, 215 
Astragalus, 85, 86 
Atlas, 57 
Auditory bulla, 45 

nerve, 240 

organ, 237 
Aves, 19 
Axis, 59 
Axis-cylinder process, 208 

B. 

Basal ganglia, 198 
Bicuspid valve, 141 
Bile, 134 

Binomial nomenclature, 20 
Bladder, 176 
Blood-vessels, 143 

injection of, 21 
Body of vertebra, 59 
Bone structure, 39 
Bones, 41 

ear, 238 

head, 41 

kinds of, 36, 38 

pelvic limb, 79 

preparation of, 27 

sesamoid, 36 

table of, 37 

terms used in describing, 36, 38 

thoracic limb, 67 
Brachia, 199 
Brachial plexus, 220 
Brachio-cephalic artery, 143 
Brachium conjunctivum, 201 
Brain, 186 

arteries of, 146 

external features, 187 

fiber- tracts of, 213 

fissures, 188 

internal structure, 192 

ventricles of, 197 
Broad ligament, 136 
Bronchus, 170 
Buccal cavity, 117 



C. 



Calcaneum, 85 
Canalis centralis, 



206 



Canidae, 19 
Cannon bone, 76 
Cannula, 21 
Capillaries, 30, 159 
Capsular ligament, 90 
Cardiac plexus, 128 
Carnivora, 19 
Carotid artery, 143 
Carpalia, 74 
Carpus, 72, 75 
Cartilage, 29 

semilunar, 91 
Caudad, 38 
Caudal, 38 
Cells, 28, 29 

gastric glands, 129 

nerve, 208 
Central nervous system, 186 

preparation for dissection, 26 
Cephalad, 38 
Cephalic, 38 
Cerebellum, 203 
Cerebrum, 188 
Chevron bones, 62 
Chief motor tract, 214 
Choroid membrane, 235 

plexus, 193 
Cilia, 170 

Circle of Willis, 147 
Circulatory system, 140 
Classes of vertebrates, 19 
Classification of animals, 18 
Clavae, 202 
Clavicle, 68 
Claws, 34 
Clinoid plate, 49 

processes, 49 
Clitoris, 178 
Cloaca, 184 
Coccyx, 63 
Cochlea, 40, 239 
Coeliac axis, 144 
Colon, 128 

Columns of spinal cord, 206 
Commissures of brain, 194 
Condyle, 39 
Conjunctiva, 233 
Connective tissue, 29 
Convolutions of brain, 188 
Coracoid process, 68, 69 
Cornu Ammonis, 196 
Corona radiata, 215 
Corpora albicantia, 191 

quadrigemina, 198 

striata, 200 



INDEX. 



245 



Corpus callosum, 196 

dentatum, 203 

geniculatum, 199 
Cotyloid bone, 79 
Cranial nerves, 215 
Cranium, 41 
Cribriform plate, 43, 44 
Cricoid cartilage, 169 
Crossed pyramidal tract, 212 
Crucial ligaments, 91 
Crura cerebelli, 203 

cerebri, 191 
Crus, 83, 84 

ad pontem, 203 
Crystalline lens, 236 
Cuboid, 86 
Cuneiform, 74 

Cutaneous sense organs, 231 
Cystic duct, 134 

D. 

Deciduous teeth, 122 
Decussation of pyramidal tract, 212 
Dendrites, 208 
Dentition, deciduous, 122 

mammalian, 123 

of cat, 120 
Dermis, 33 
Diarthroses, 89 
Diastema, 55 
Diencephalon, 187 
Digestion, organs of, 117 
Digestive system of mammals, 137 
Digitigrade, 78 
Digits, 76, 81, 86 
Dissection, directions for, 95 
Distad, 38 
Distal, 38 
Distribution, 18 
Ductless glands, 165 
Ductus communis choledochus, 128, 

134 
Duodenum, 126 
Dura mater, 186, 205 



Ear, 237 

Ectocuneiform, 86 
Embryology, 17 
Endomysium, 93 
Endoskeleton, 32 
Entocuneiform, 86 
Epidermis. 33 



Epididymis, 182 
Epiglottis, 169 
Epimysium, 93 
Epiphysis, 39 
Epithelium, 28, 29 
Esophagus, 126 
Ethmoid bone, 42 
Ethmoturbinal, 42, 44 
Eustachian tube, 45, 124 
Excretion, 30 
Excretory system, 174 
Exoskeleton, 32 
External capsule, 201 
Eye, 233 

F. 

Face, 41 

Falciform ligament, 133 

Fallopian tubes, 177 

Falx cerebri, 186 

Families, 19 

Fascia, 94 

Fasciculus of Burdach, 211 

of Goll, 211 

of muscle, 94 
Fauces, 117 
Female organs, 177 
Femur, 81 
Fenestra ovalis, 45 

rotundum, 45 
Fiber tracts of nervous system, 210 
Fibers, 29, 30 

of brain, 213 
Fibula, 84 
Fillet, 215 

Fissures of brain, 188 
Foot, arteries of, 153 

bones of, 85 

muscles of, 109, 111 

nerves of, 224 
Foramen, 39 

anterior palatine, 51 

infraorbital, 52 

intervertebral, 62 

jugular, 48 

lacerum, 48, 50 

magnum, 46 

mental, 55 

obturator, 81 

of Monro, 193 

optic, 51 

ovale, 51 
Foramina, table of, 49 
Formaldehyde, 20, 96 
Fossa, 39 



246 



INDEX. 



Frena, 119 
Frontal bones, 41 
Funiculi gracilis, 2 1 1 

of Goll and Burdach, 211 
Funiculus cuneatus, 202 

of Rolando, 202 

G. 

Gall-bladder, 126 
Gall-cyst in mammals, 138 
Ganglia, 218, 219, 227 
Gasserian ganglion, 218 
Gastric glands, 129 
Genera, 19 
Ginglymus, 90 
Gland, Cowper's, 183 

lachrymal, 234 

mammary, 180 

parotid, 132 

prostate, 183 

salivary, 131 

thymus, 166 

thyroid, 166 
Glands, accessory, 131 

Harderian, 234 

lymph, 162 

Meibomian, 234 

of mouth, 119 

of small intestine, 130 

of stomach, 129 

sebaceous, 33, 174 

sudoriparous, 34, 174 
Glenoid cavity, 55, 67 
Graafian follicle, 179 
Great splanchnic nerve, 228 
Gustatory organ, 232 
Gyri of brain, 188 



H. 

Habena, 200 

Hair, 34 

Haversian canals, 40 

Heart, 140 

Hepatic duct, 134 

Hippocampus major, 196 

Histology, 17 

Horns of mammals, 41 

Humerus, 69 

Humors of eye, 236 

Hymen, 178 

Hyoid bones, 55 

Hypogastric plexus, 230 

Hypophysis, 191 



I. 

Ileum, 128 
Ilium, 79 
Infundibula, 172 
Infundibulum, 191 
Inguinal canal, 182 
Injection of vessels, 20 
Innominate bone, 79, 81 
Integument, 33 
Internal capsule, 201, 205, 212 

malleolus, 84 
Interparietal, 46 
Intestine, 126 
Iris, 235 
Ischium, 79 
Iter or aqueduct of Sylvius, 193 

J- 

Jar, preservation, 20 
Jejunum, 126, 128 
Joints, 89 



Kidney of cat, 

of mammals, 

Knee-joint, 90 



K. 

175 
184 



L. 



Lachrymal bone, 53 
Lacteals, 130, 161 

injection of, 25 
Lacunae, 40 
Lambdoidal ridge, 48 
Larynx, 55, 168 
Laterad, 38 
Leg, arteries of, 151 

bones of, 79 

muscles of, 108 

nerves of, 224 
Ligaments, 29 

of knee-joint, 91 

of larynx, 135 
Linea aspera, 82 
Liver, 133 
Lumbar plexus, 223 
Lungs, 172 
Lymph, injection of, 24 

system, 161 

M. 

Malar bone, 54 

gland, 132 
Male organs, 180 



-» ' j- ~ 



INDEX. 



247 



Malpighian bodies, 175 
Mandible, 54 
Marrow, 40 
Marsupialia, 19 

urogenital system of, 184 
Mastoid portion of temporal, 45 
Maxilla or maxillary, 52 
Maxilloturbinal, 53 
Meatus auditorius externus, 45, 237 

internus, 46 
Median nerve, 222 
Mediastinum, 172 
Medulla oblongata, 202 
Membranes, mucous, 129, 137, 232 

of brain, 186 

of cord, 205 

serous, 136 
Meninges, 186, 205 
Meniscus, 90 
Mesad, 38 
Mesal, 38 

Mesencephalon, 187, 188 
Mesenteries, 135 
Mesethmoid, 43 
Mesocuneiform, 86 
Metacarpus, 75 
Metatarsus, 86 
Mitral valve, 141 
Morphology, 17 
Motor decussation, 213 
Mouth, 117 

Mucous membrane, 129, 137, 232 
Muscles, dissection of, 95 

eye, 233 

head and neck, 97 

kinds, 93 

naming of, 94 

pelvic limb, 108 

table of, 97 

thoracic limb, 100 
Musculospiral nerve, 221 

Names, scientific, of animals, 20 
Nares, 124 
Nasal bone, 53 

chamber, 53 

duct, 233 

septum, 43 
Navicular, 85 
Nerve, abducens, 217 

anterior crural, 224 

auditory, 217 

facial, 217 



Nerve, glossopharyngeal, 217 

hypoglossal, 217 

iliohypogastric, 223 

interosseous, 222 

lumbo-inguinal, 223 

mandibular, 217 

maxillary, 217 

median, 222 

musculocutaneous, 224 

musculospiral, 220, 222 

obturator, 224 

oculomotor, 217 

olfactory, 217 

ophthalmic, 217 

optic, 217 

pathetic or trochlear, 217 

peroneal, 225 

phrenic, 228 

plantar, 224 

radial, 222 

saphenous, 224 

sciatic, 224, 226 

splanchnic, 228 

subscapular, 221 

thoracic, 221 

tibial, 224 

trigeminal, 217 

ulnar, 222 

vagus, 217, 228 
Neural arch, 57 

canal, 59 
Nomenclature, 20 
Nucleus caudatus, 201 

cuneatus, 211 

gracilis, 2 1 1 

lenticularis, 201 



O. 

Obturator foramen, 81 

nerve, 224 
Occipital bone, 46 
Olfactory organ, 232 
Omentum, 135 
Ontogeny, 17 

Optic commissure (chiasm), 191 
195 

nerve, 217 

thalami, 199 
Orbital plate, 52 
Orders of mammals.. 19 
Organ, 28 

of Corti, 240 
Organs of sense, 231 
Ornithodelphia, 19 



248 



INDEX. 



Ornithodelphia, brain of, 241 
urogenital system, 184 

Os ealcis, 85 
magnum, 75 
planum, 43 

Osseous system, 31 

Ova of mammals, 179 

Ovaries, 178 

Oviparous, 19 

P. 

Pacinian corpuscle, 232 
Palatine bone, 52 

plate, 52 
Pancreas, 135 
Papillae of tongue, 233 
Parietal bone, 46 
Parotid gland, 132 
Patella, 83 - 

ligaments of, 90 
Peduncles of cerebellum, 203 

of cerebrum. 191, 213 
Penis, 183 
Pericardium, 140 
Perimysium, 94 
Periosteum, 40 
Peripheral nerves, 216 
Peritoneum, 135 
Petrous bone, 45 
Phalanges, 76, 87 
Pharynx, 124 
Phytogeny, 18 
Physiology, 17 
Pia mater, 186, 205 
Pillar of fauces, 1 1 7 
Pineal body, 200 
Pisces, 19 
Pisiform bone, 74 
Pituitary body, 191 
Plantigrade, 78 
Pleura, 172 
Plexus, brachial, 220 

cardiac, 228 

cervical, 219 

choroid, 193, 194 

lumbar, 223 

pulmonary, 228 

sacral, 226 

solar, 229 
Pons Varolii, 188, 195 
Portal system, 156 
Premaxillary (premaxilla), 51 
Preservation of material, 20 
Primates, 19 



Process, acromion, 68 

clinoid, 49 

coracoid, 68 

coronoid, 70 

hamular, 51 

mammillary, 61 

mastoid, 47 

odontoid, 60 

postorbital, 41 

pterygoid, 51 

spinous, 57 

styloid, 70, 71 

transverse, 57 

trochanter, 81, 82 
Projection fibers, 213 
Prostate gland, 183 
Proximad, 38 
Psychology, 18 
Pterygoid bone, 48, 51 
Pulmonary arteries, 142 

circulation, 143 

veins, 159 



Quadriceps extensor muscle, 110 

R. 

Radius, 70 

Rectum, 128 

Reproductive svstem, 174 

Reptilia, 19 

Restiform body, 202, 204 

Retina, 236 

Ribs, 65 

Rodentia, 19 

Roots of spinal nerves, 206 

Rotatoria, 90 

Round ligament, 136 



Sacral plexus, 226 

Sacrum, 62 

Sagittal, 38 

Salivary glands, 131 

Saphenous nerve, 224 

Sarcolemma, 93 

Scapholunar, 74 

Scapula, 67 

Schneiderian membrane, 239 

Sciatic nerve, 224, 226 

notch, 80 
Scrotum, 180 
Sebaceous glands, 174, 



INDEX. 



249 



Secondary motor tract, 215 
Semicircular canals, 239 
Semilunar ganglion, 230 

valves, 142 
Sensory tract of brain, 215 
Septum lucidum, 196 
Serous membrane, 136 
Sesamoid bones, 36, 76 
Shaft, 39 

Shoulder girdle of mammals, 69 
Sigmoid cavity, 70 
Sinuses, blood, 157 
Sirenia, 19 
Skeleton, 36 
Skin, 32 

Solar plexus, 229 
Species, 19 
Spermatic cord, 181 
Sphenoid bone, 48 
Sphincter muscle, 194 
Spinal cord, 205 

preparation for dissection, 26 

nerves, 218 
vSpleen, 165 
Stenson's duct, 132 
Sternebra, 63 
Sternum, 63 
Stomach, 126 

of ruminant, 137 
Subclasses of mammalia, 19 
Subclavian artery, 143 

vein, 156 
Sublingual gland, 132 
Submaxillary gland, 132 
Sudoriparous glands, 174 
Sulci of brain, 188 
Superior pyramidal decussation, 

215 
Suprarenal bodies (capsules), 167 
Sutures, 89 

Sympathetic nervous system, 226 
Symphysis of mandible, 54 

pubis, 80 
Synarthroses, 89 
Synovia, 90 

Synovial membrane, 91 . 
Syringe, injecting, 21 
Systemic circulation, 143 
Systems of mammals, 28 



T. 



Tarsalia, 86 
Tarsus, 84 
Taste-buds, 233 



Taxonomy, 18 
Teeth, 120 

of mandible, 54 

of maxillary, 52 

of premaxillary, 51 
Telencephalon, 187 
Temporal bone, 44 
Tendon, 93 
Tentorium, 46 
Testes, 180 
Thoracic aorta, 143 

cavity, 125 

duct, 165 

nerves, 219 
Thymus gland, 125, 166 
Thyroid cartilage, 169 

gland, 166 
Tibia, 83 
Tissues, 29 
Toes, 87 
Tongue, 119 
Tonsil, 119 
Trachea, 170 
Tracts of spinal cord, 215 
Trapezium, 74 
Trapezoid, 74 
Tricuspid valve, 141 
Tuber cinereum, 191 
Tuberosity, 39 
Turbinated bones, 53 
Tympanum, 237 



Ulna, 70, 71, 72 
Ulnar nerve, 222 
Unciform, 75 
Ungulata, 19 

digits of, 77 

origin of, 71 
Unguligrade, 78 
Ureter, 176 

Urogenital system of mammals, 184 
Ursidae, 19 
Uterus, 177 



V. 

Vagina, 178 
Valves, heart, 141 

of arteries, 143, 154 

of veins, 154 
Varieties, 19 
Vas deferens, 182 
Vascular system, 140 



2^0 



INDEX. 



156 



156 



Vascular system, preparation 

for dissection, 20 
Vein, azygos, 156 

brachiocephalic, 

cephalic, 154 

coronary, 156 

gastroepiploica, 

gastrosplenic, 156 

hepatic, 154 

iliac, 156 

iliolumbar, 155 

jugular, 1 5 1 

maxillary, 157 

mesenteric, 156 

ovarian, 155 

pancreatoduodenalis, 156 

phrenic, 154 

portal, 156 

postcava, 154 

precava, 154 

pulmonary, 159 

saphenous, 154 

spermatic, 155 

sternal, 156 

subclavian, 157 

suprarenal, 155 

vertebral, 156 
Veins, structure of, 154 

trunk, head, and neck, 155 

valves of, 154 
Velum interpositum, 193 

palati, 117 



of. Vena cava, 156 

Venous sinuses, 157 

system, 153 
Ventricles of brain, 192 
Vertebra. : J 

caudal, 62 

cervical, 58 

lumbar, 61 

thoracic, 60 
Yertebrarterial canal, 59 
Yertebrata, 19 
Villi, 130 
Viscera, 124 
Visual organ, 233 
Vital knot, 2 : 2 
Viviparous, 1S4 
Vocal cords, 169 
Vomer, 52 

W. 

Wharton's duct, 132 
Willis, circle of, 147 

X. 

Xiphoid prices;. 63 

Z. 

Zygoma, 44, 54 
Zygomatic gland, 132 
process, 44 



MEDICAL 
BOOKS 



Note Subject Index, Page 6 




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SUBJECT INDEX. 



Gould's Medical Dictionaries, - Pages 12, 13 
Morris' Anatomy, New Edition, - - Page 4 
Compends for Students, - Page 27 



SUBJECT. PAGE 

Alimentary Canal (see Sur- 
gery) 24 

Anatomy 7 

Anesthetics 18, 19 

Autopsies (see Pathology) 20 

Bacteriology 8 

Bandaging (see Surgery) . . 24 | 

Blood, Examination of . . . 8 

Brain 8 

Chemistry. Physics 9 

Children, Diseases of 11 

Climatology 19 

Clinical Charts 25 

Compends 27 

Consumption (see Lungs) . 16 

Cyclopedia of Medicine. . . 13 

Dentistry 11 

Diabetes (see Urin. Organs) 25 

Diagnosis 11 

Diagrams (see Anatomy) . 8 

Dictionaries, Cvclopedias. 12 

Diet and Food 13 

Disinfection 16 

Dissectors 7 

Ear 14 I 

Electricity 14 [ 

Embryology 7 

Emergencies 24 

Eye 14 

Fevers 15 

Food 13 

Formularies 21 

Gvnecology 15 

Hav Fever 25 

Heart 15 

Histology 15 

Hydrotherapy 19 

Hygiene 16 

Hypnotism 8 

Insanity 8 

Intestines 23 

Latin, Medical (see Phar- 
macy) 21 

Life Insurance 19 

Lungs 16 

Massage 17 

Materia Medica 17 

Mechanotherapy 17 

Medical Jurisprudence. ... 18 



SUBJECT. PAGE 

Mental Therapeutics 8 

Microscopy 18 

Milk 8, 10 

Miscellaneous 18 

Nervous Diseases 19 

Nose 25 

Nursing 20 

Obstetrics 20 

Ophthalmology 14 

Organotherapy 18 

Osteology (see Anatomy) . 7 

Pathology 20 

Pharmacy 21 

Physical "Diagnosis 11 

Physical Training 17 

Physiology 22 

Pneumotherapy 19 

Poisons (see Toxicology) . . 18 

Practice of Medicine 22 

Prescription Books (Phar- 
macy) 21 

Refraction (see Eye) 14 

Rest 19 

Sanitary Science 16 

Serum-Therapy 17 

Skin 23 

Spectacles (see Eye) 14 

Spine (see Nervous Dis- 
eases) 19 

Stomach 23 

Students' Compends 27 

Surgery and Surgical Dis- 
eases 24 

Technological Books 9 

Temperature Charts 25 

Therapeutics 17 

Throat 25 

Toxicology 18 

Tumors (see Surgery) .... 24 

U. S. Pharmacopoeia 22 

Urinary Organs 25 

Urine 25 

Venereal Diseases 26 

Veterinary Medicine 26 

Visiting Lists, Physicians'. 
(Send for Special Circu- 
lar.) 

Water Analysis 16 

Women, Diseases of 15 



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ANATOMY. EMBRYOLOGY. 

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DAVISSON. Mammalian Anatomy. With Special Reference 
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YUTZY. Guide to the Dissection of the Human Body. Based 
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LEFFMANN. Compend of Medical Chemistry, Inorganic and 
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LEFFMANN. Analysis of Milk and Milk Products. 2d Edition, 
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LEFFMANN. Water Analysis. For Sanitary and Technic Pur- 
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LEFFMANN AND BEAM. Select Methods in Food Analysis. 
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RICHTER. Inorganic Chemistry. 5th American from 10th 
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SMITH. Electro-Chemical Analysis. 3d Ed. 39 Illus. $1.50 

SMITH AND KELLER. Experiments. Arranged for Students 
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SUTTON. Volumetric Analysis. A Systematic Handbook for 
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SYMONDS. Manual of Chemistry. 2d Edition. $2.00 

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MEDICAL BOOKS. 11 



THRESH. Water and Water Supplies. 3d Edition. $2.00 

ULZER AND FRAENKEL. Chemical Technical Analysis. 

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WOODY. Essentials of Chemistry and Urinalysis. 4th Edition. 

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POWER. Surgical Diseases of Children and their Treatment 
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STARR. The Digestive Organs in Childhood. The Diseases of 
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STARR. Hygiene of the Nursery. Including the General Regi- 
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SMITH. Wasting Diseases of Children. 6th Edition. $2.00 
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DIAGNOSIS. 

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DA COSTA. Clinical Hematology. A Practical Guide to Exam- 
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EMERY. Bacteriological Diagnosis. 2 Colored Plates and 32 
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PERSHING. Diagnosis of Nervous and Mental Diseases. 
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DENTISTRY. 

Special Catalogue of Dental Books sent free upon application. 
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12 SUBJECT CATALOGUE. 

BROOMELL. Anatomy and Histology of the Human Mouth 
and Teeth. Second Edition, Revised and Enlarged. 337 
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FILLEBROWN. Operative Dentistry. Illustrated. $2.25 

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GORGAS. Questions and Answers for the Dental Student. 
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HARRIS. Principles and Practice of Dentistry. Including 
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HARRIS. Dictionary of Dentistry. Including Definitions of Such 
Words and Phrases of the Collateral Sciences as Pertain to the 
Art and Practice of Dentistry. 6th Edition, Revised and 
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RICHARDSON. Mechanical Dentistry- 7th Edition. Thor- 
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SMITH. Dental Metallurgy. 2d Edition. Illustrated. $2.00 

TAFT. Index of Dental Periodical Literature. $2.00 

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DICTIONARIES. CYCLOPEDIAS. 

GOULD. The Illustrated Dictionary of Medicine, Biology, and 
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those Sciences Collateral to it: Biology (Zoology and Botany), 
Chemistry, Dentistry, Pharmacology, Microscopy, etc., with 
many useful Tables and numerous fine Illustrations. 1633 
pages. Fifth Edition. 

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GOULD. The Medical Student's Dictionary, nth Edition. Il- 
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MEDICAL BOOKS. 13 

GOULD. The Pocket Pronouncing Medical Lexicon. 4th Edi- 
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14 SUBJECT CATALOGUE. 

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MEDICAL BOOKS. 15 

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16 SUBJECT CATALOGUE. 

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MEDICAL BOOKS. 17 



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18 SUBJECT CATALOGUE. 

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WHITE AND WTLCOX. Materia Medica, Pharmacy, Pharma- 
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MEDICAL BOOKS. 19 



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NURSING (see also Massage). 

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WINCKEL. Text-Book of Obstetrics, Including the Pathology 
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PATHOLOGY. 

BLACKBURN. Autopsies. A Manual of Autopsies Designed 
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MEDICAL BOOKS. 21 



COPLIN. Manual of Pathology. Including Bacteriology, Tech- 
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DA COSTA. Clinical Hematology. A Practical Guide to the 
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COBLENTZ. Volumetric Analysis. Illustrated. $1.25 

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GREENISH. Microscopical Examination of Foods and Drugs. 
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ROBINSON. Latin Grammar of Pharmacy and Medicine. 4th 
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SAYRE. Organic Materia Medica and Pharmacognosy. An 
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macal Botany. With sections on Histology and Microtech- 
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Cloth, $4.50 



22 SUBJECT CATALOGUE. 

SCOVILLE. The Art of Compounding. Second Edition, Re- 
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PHYSIOLOGY. 

BIRCH. Practical Physiology. An Elementary Class Book. 
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BRUBAKER. Compend of Physiology. 11th Edition, Revised 

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MEDICAL BOOKS. 23 



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MEDICAL BOOKS. 25 

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27 



DA COSTA 



Clinical Hematology 



A Practical Guide to the Examination of the Blood by 
Clinical Methods. With Reference to the Diagnosis of 
Disease. With Colored Illustrations. Cloth, $5.00 

*** A new, thorough, systematic, and comprehensive 
work, its purpose being, first, to show how to examine the 
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author's aim has been to cover not alone the field of original 
research, but to supply a book for the student, the hospital 
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wanting in none of these respects. 

OERTEL 



Medical Microscopy 



JUST READY 

A GUIDE TO DIAGNOSIS, ELEMEN- 


TARY 


LABORATORY 


METHODS, 


AND 


MICROSCOPIC 


TECHNIC 



By T. E. Oertel, M.D., 

Professor of Pathology and Clinical Microscopy, Medical Depart- 
ment, University of Georgia. 

WITH 131 ILLUSTRATIONS, izmo. Cloth, %%. 00 
23 



The Pocket Cyclopedia, of 
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Uniform <o)Uh "Gould's Pocket Dictionary" 



A concise practical volume of nearly 600 
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It is Multum in Parvo. Sample Pages Free. 
29 



A NEW EDITION 



Crocker on the Skin 



The Diseases of the Skin. Their Description, Pathology, 
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STURGIS— MANUAL OF 
VENEREAL DISEASES 



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FOR THE DISSECTING ROOM 

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A Manual of the Dissections of the Human Body. By John 
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31 



EDGAR'S 

OBSTETRICS 

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OCTAVO. CLOTH, $6.00; SHEEP, $7.00 



T 



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